Hardy worked as a jobber for the World Wrestling Federation (WWF) from 1994 up until he signed a full-time contract. His first WWF match was against Nikolai Volkoff on May 23, 1994, which he lost by submission He wrestled sporadically throughout 1994 in the WWF, losing matches against Crush, Razor Ramon, Owen Hart and The Undertaker. Hardy continued wrestling with the WWF sporadically, including matches against Hunter Hearst Helmsley and "The Ringmaster" Steve Austin. It was not until 1998, however, that the Hardy brothers were given full-time WWF contracts, and sent to train with former wrestler Dory Funk, Jr.. The Hardy Boyz used a cruiserweight, fast-paced high flying style in their matches, often leaping from great heights to do damage to their opponents (and themselves in the process). Although Jeff was better known for his extreme moves, Hardy was a prodigious high-flier himself. In 1999, while feuding with Edge and Christian, the duo briefly picked up Michael Hayes as a manager. On July 5, they won their first WWF Tag team Championship by defeating the Acolytes, but lost it back to them a month later. They soon dumped Hayes however, and joined the short lived stable The New Brood. After breaking away from Gangrel, Hardy and Jeff were briefly managed by Terri Runnels, after they won her services in the first ever tag team ladder match.
In 2000, the Hardy Boyz found a new manager in their real-life friend Lita. Together, the three became known as "Team Xtreme". Throughout 2000 they continued feuding with Edge and Christian, defeating them for the WWF Tag Team Titles on two occasions. Hardy won the WWE Hardcore Championship on April 24, 2000, on Raw is War, by defeating Crash Holly, but lost it back to Holly three days later on SmackDown!. At SummerSlam the Hardy Boyz competed in the first ever Tables, Ladders, and Chairs match, for the Tag Team Titles against the Dudley Boyz and Edge and Christian, but were unsuccessful.
In 2001, after Jeff's Intercontinental Championship run, Hardy was given a singles championship push. He won the European Championship on SmackDown! four days before Backlash. Hardy believes that he was pushed to win the title because of Jeff winning the Intercontinental Championship, and because of the effort he put into his previous storyline with Triple H and Stone Cold Steve Austin. He became the second-longest reigning European Champion in history and the longest-reigning American-born European Champion.
Throughout the year, the Hardy Boyz continued to win as a tag team, winning the WWF Tag Team Titles two more times, and the WCW Tag Team Titles during the Invasion. By the end of the year, the Hardy Boyz began a storyline where they were having trouble co-existing. This culminated in a match between the two, with Lita as the guest referee, at the Vengeance pay-per-view, which Jeff won.
At the beginning of 2002, it seemed Team Xtreme had patched things up. After the Brand Extension, however, Hardy was relegated to Heat while Jeff wrestled on the main show, Raw. On the August 12 episode of Raw, Hardy turned against Jeff during Jeff's match against Rob Van Dam, because Hardy was frustrated at not receiving a match against Van Dam for the number one contendership for the Intercontinental Championship. A short time later, Hardy joined the SmackDown! roster. On the October 3 episode of the show, Hardy took advantage of a run-in from Brock Lesnar to defeat The Undertaker.
Having now dubbed himself "Matt Hardy: Version 1", and with his MF'er (Mattitude Follower) Shannon Moore in his corner, 2003 began with Hardy frantically trying to lose weight to get under the 220 lb (100 kg) weight limit to compete for the WWE Cruiserweight Championship. After just barely making weight, Hardy defeated Billy Kidman at No Way Out to win the Cruiserweight title. At WrestleMania XIX, he successfully defended it against Rey Mysterio. The Mattitude faction then expanded to include Crash Holly as Moore's "Moore-on" (follower). He later disbanded the group and returned to Raw in order to be able to travel and work with his then girlfriend Lita, who just returned from an injury. On his first night back, he turned on Lita in storyline after teasing a proposal to her. Hardy spent little time on Raw and later turned into a fan favorite by engaging in a rivalry with Kane. Lita was also involved in the storyline, and Hardy took time off after a chokeslam from Kane off the stage during Lita and Kane's wedding. This time off was due to a knee injury.
On July 11, 2005, Hardy posted on his website that he was finally "free", that wrestling fans had not seen the last of him, and that he had a surprise for the fans who had supported him. That night on Raw, Hardy attacked Edge backstage and again later during Edge's match with Kane, leaving the commentators speechless. Before being escorted out of the building by security, Hardy stated that Edge and Lita would pay for their actions and told fans that they could see him at Ring of Honor. Hardy also called out Johnny Ace as he made his way out. This caused an uproar amongst fans, who were confused and wondered if the whole thing was a work or a shoot. Similar occurrences repeated during the following two weeks.
On the August 1 episode of Raw, Vince McMahon officially announced Hardy's return to WWE, adding that Hardy would face Edge at SummerSlam. Hardy made his in-ring return, defeating Snitsky on the August 8 Raw. Seconds after the victory, Hardy was attacked by Edge, and as he was being carried backstage, Matt counterattacked Edge in the locker room. On August 21 at SummerSlam, their match came to a premature end when Edge dropped Hardy onto the top of a ring post, causing him to bleed heavily. The referee ended the match on the grounds that Hardy could not continue, and Edge was declared the winner. After SummerSlam, the two continued fighting on Raw, including a Street Fight that resulted in Hardy performing a Side Effect on Edge off the entrance stage and into electrical equipment below. At Unforgiven, Edge faced Hardy in a steel cage match. Hardy caught an interfering Lita with the Twist of Fate and won the match with a leg-drop off the top of the cage. Hardy and Edge faced each other at WWE Homecoming in a Loser Leaves Raw ladder match. Edge's briefcase holding the contract for his WWE World title shot was suspended above the ring. The winner of the match received the contract and the loser was forced to leave Raw. After a contentious match, Edge tied Hardy's arms in the ropes, and Lita trapped Hardy in a crucifix hold, leaving Hardy only able to watch Edge win. When the match ended, Edge and Lita gloated over the victory, but Hardy took it in stride and left the arena. With his defeat at the hands of Edge, Hardy was moved to the SmackDown! brand where he re-debuted with a win over Simon Dean on October 21 in Reno, Nevada.
Back on SmackDown!, Hardy started an angle with MNM (Johnny Nitro and Joey Mercury) and their manager Melina when Melina approached Hardy, seemingly wanting Hardy to join with her team. Hardy refused the offer, which led to him facing the tag team on several occasions with a variety of partners. One of his partners, Road Warrior Animal, brutally attacked him after they were defeated – sick of "pulling all the weight in tag teams". Animal, who was renamed The Road Warrior, and Hardy feuded for a while after this, with Hardy picking up several wins over the veteran, including a qualifying match for the Money in the Bank ladder match at WrestleMania 22, which was ultimately won by Rob Van Dam.
Hardy next competed in the SmackDown! King of the Ring tournament, losing to eventual winner Booker T in the opening round thanks to a low blow and distraction from Sharmell. Hardy also became the first man to defeat Mr. Kennedy. On July 25, after the SmackDown! taping, Hardy was taken out of action after doctors found the remnants of the staph infection that had plagued him the previous year. He was sidelined until August 25 while he healed. Hardy made a surprise appearance backstage at Unforgiven after Jeff's match against Johnny Nitro. Lita joined the two in the segment, making this the first time the three had been seen together on WWE television since February 2003. Hardy then began a rivalry against Gregory Helms which saw both winning over each other time and time again. Then at No Mercy, in both of their hometown, Cameron, North Carolina, Hardy beat Helms. The two met again one more time at Survivor Series, where Hardy's team won in a clean sweep.
On the November 21, 2006 episode of ECW on Sci Fi, Hardy and Jeff competed in a match together for the first time in almost five years, defeating the Full Blooded Italians. At Survivor Series, the Hardy Boyz competed with CM Punk and D-Generation X (Triple H and Shawn Michaels) as part of Team DX versus Team Rated-RKO (which included Edge, Randy Orton, Johnny Nitro with Melina, Mike Knox, and Gregory Helms) in a traditional Survivor Series match. Team DX won with a shut out, last eliminating Orton. At December to Dismember, the Hardy Boyz issued an open challenge to any tag team who wanted to face them. MNM answered their challenge by reuniting at December to Dismember, but ultimately lost to the Hardy Boyz. At Armageddon, Hardy and Jeff competed against Paul London and Brian Kendrick, MNM, and Dave Taylor and William Regal in a Ladder match but lost. Subsequently, he and Jeff feuded with Joey Mercury and Johnny Nitro after the legitimate incident where they injured Mercury's face at Armageddon 2006. This led to a bitter long term rivalry, and at the 2007 Royal Rumble, Hardy and Jeff defeated MNM. Mercury and Hardy continued to feud until Mercury was released from WWE in March. Before Mercury's release, however, Hardy defeated him to earn a spot in the Money in the Bank ladder match at WrestleMania 23, which was ultimately won by Mr. Kennedy.The next night on Raw, the Hardys competed in a 10-team battle royal for the World Tag Team Championship. They won the titles for the sixth time after last eliminating Lance Cade and Trevor Murdoch. After briefly feuding with Cade and Murdoch, the Hardys retained their World Tag Team Championship in their first title defense at Backlash. On the June 4 episode of Raw, however, The Hardys lost their titles to Cade and Murdoch, after Murdoch pushed Jeff's foot off the bottom rope during Cade's pinfall, causing the three count to continue.
On the July 6, 2007 episode of SmackDown!, Hardy won a non-title match against WWE United States Champion Montel Vontavious Porter (MVP), which resulted in a feud between the two. Hardy was unable to defeat MVP at The Great American Bash for the WWE United States Championship. MVP then claimed that he was "better than Hardy at everything", which led to a series of contests between Hardy and MVP, such as a basketball game, an arm wrestling contest, and a chess match which MVP "sneezed" on and ruined when Hardy put him in check. MVP challenged Hardy to a boxing match at Saturday Night's Main Event, however MVP was legitimately diagnosed with the heart condition Wolff-Parkinson-White syndrome. Since MVP was unable to compete, Hardy faced his replacement, former world champion boxer, Evander Holyfield. The match ended in a no contest after MVP entered the ring to verbally abuse Holyfield, who then knocked him out. MVP also challenged Hardy to a beer drinking contest at SummerSlam, but as revenge for what happened at SNME, Hardy allowed Stone Cold Steve Austin to replace him; Austin simply performed a stunner on MVP then kept drinking.
After a segment involving MVP inadvertently choosing Hardy as his tag-team partner, Theodore Long promptly set up a match against Deuce 'n Domino for the WWE Tag Team Championship which the duo were able to win, therefore setting up Hardy's first reign as WWE Tag Team Champion. It was the first time Hardy held a tag team championship with someone other than his brother. Hardy and MVP retained the titles at Unforgiven in a rematch against former champions Deuce 'n Domino. Hardy was scheduled to face MVP at Cyber Sunday, but due to a head injury sustained on the previous episode of SmackDown!, he was not medically cleared to compete.
On the November 16 episode of SmackDown!, Hardy and MVP dropped the WWE Tag Team Championship to John Morrison and The Miz. Despite the fact that Hardy was hurt, MVP immediately invoked the rematch clause. After the rematch, in which Hardy was forced to tap out, MVP attacked Hardy, repeatedly targeting his knee. It was later confirmed by WWE.com that Hardy had suffered an injury at his former partner's hands and that he might not be able to compete at Survivor Series. Despite his absence at the pay-per-view, his team was able to win the match. On November 21, WWE's official website reported that Hardy underwent an emergency appendicectomy in Tampa, Florida. A CT scan revealed an inflamed appendix after Hardy was feeling extreme pain. Later surgery revealed that his appendix had already burst. According to Hardy himself, on December 8 doctors back in North Carolina found an abscess of infection that had not been caught, and he had it drained, spending an additional several days in the hospital. Hardy made an appearance at the December 31 episode of Raw supporting his brother Jeff. To further Jeff's storyline with Randy Orton, however, Hardy was attacked by Orton. Hardy made his return at a live event in Muncie, Indiana on March 1, 2008.
On March 30, 2008, at WrestleMania XXIV, Hardy made his televised return to WWE programming in the Money in the Bank ladder match by cutting through the crowd, and attacking MVP to prevent him from winning the match. He made his official in-ring return the next night on Raw, losing a singles match to WWE Champion Randy Orton. On the April 4 episode of SmackDown!, Hardy faced MVP in a non-title match, which he won, re-igniting their storyline rivalry. On April 27, 2008, Hardy defeated MVP to win the United States Championship at Backlash.After some sporadic feuds for the title, Hardy was drafted to the ECW brand on the June 23, 2008 episode of Raw during the 2008 WWE Draft, in the process making the United States Championship exclusive to ECW. After a successful title defense against Chavo Guerrero at Night of Champions, he dropped the United States Championship to Shelton Benjamin at the Great American Bash pay-per-view on July 20, 2008, which meant that the title returned to SmackDown.
On the July 22 episode of ECW, Hardy became the number one contender to Mark Henry's ECW Championship after defeating John Morrison, The Miz and Finlay in a Fatal Four-Way match. He won the title match at SummerSlam by disqualification due to interference from Henry's manager, Tony Atlas, thus he failed to win the title. Due to the ending of the pay-per-view match, Hardy received a rematch for the title on the next episode of ECW, but again failed to win the title when Henry pinned him after a distraction by Atlas.
At Unforgiven, Hardy won the ECW Championship during the Championship scramble match, defeating then-champion Henry, The Miz, Finlay and Chavo Guerrero by pinning the Miz with three minutes left, thus making Hardy the first person in history to win a championship scramble in WWE, and marking his first world heavyweight championship win. He continued to feud with Henry until No Mercy, where Hardy successfully retained the title. After successful defenses against Henry, Chavo, Finlay, and Evan Bourne, Hardy lost the title to Jack Swagger on the January 13, 2009 episode of ECW, which was taped on January 12.
At the 2009 Royal Rumble pay-per-view, after losing an ECW Championship rematch to Swagger, Hardy turned into a villain when he hit his brother Jeff with a steel chair, allowing Edge to win the WWE Championship. On the January 27, 2009 episode of ECW, it was announced by General Manager Theodore Long that Hardy had requested, and been granted, his release from ECW, and had re-signed with the SmackDown brand. As part of the buildup to this feud, Hardy implied that he was responsible for all of Jeff's accidents leading back to November, including an automobile accident and a pyrotechnics accident, in an attempt to stop Jeff holding the WWE Championship, and at WrestleMania XXV, Hardy defeated Jeff in an Extreme Rules match, and in a stretcher match on the following episode of SmackDown.On the April 13 episode of Raw, Hardy was drafted to the Raw brand as part of the WWE draft. Two weeks later, in a rematch from WrestleMania, Hardy lost to Jeff in an "I Quit" match at Backlash, in which he broke his hand. Hardy continued to wrestle with his hand in a cast, incorporating it into his persona and claiming that he was wrestling under protest. At the June 22 taping of WWE Superstars, Hardy suffered an injury, when his intestines "exploded" through his abdominal wall, during a Triple Threat match against MVP and Kofi Kingston. Hardy had suffered a tear in his abdominal muscle two years previously, but had not needed surgery until it worsened, and became a danger to his health. He was then traded to the SmackDown brand on June 29, and underwent surgery for the torn abdominal muscle on July 2. He made his return on the August 7 episode of SmackDown as the special guest enforcer in the World Heavyweight Championship match between his brother, Jeff, and CM Punk, and helped Jeff retain the championship by counting the pinfall. On the August 21 episode of SmackDown, after apologizing for his past actions towards Jeff, he had his first match back after his injury when he teamed with Jeff and John Morrison to defeat The Hart Dynasty and CM Punk, in the process turning him into a fan favorite again.