After WCW was bought by the World Wrestling Federation in March 2001, Booker T made his debut at the King of the Ring pay-per-view in 2001 attacking WWF Champion Stone Cold Steve Austin during his match, promptly injuring him in his very first move in the WWF. He later turned heel and became a leading member of the The Alliance during the Invasion storyline. During July 2001, in his debut match in the company, Booker defended his WCW World Heavyweight Championship against Buff Bagwell. At InVasion, The Alliance defeated Team WWF when Steve Austin joined the Alliance. On July 26, Booker gave up his WCW United States Title and handed it over to Chris Kanyon. He later lost the WCW World title to Kurt Angle, but he went on to win the title back on the July 30 episode of Raw. Booker kept the title until SummerSlam, when he lost the title to The Rock after feuding with him over the similarity in their gimmicks and their identical finishing moves, the Book End/Rock Bottom. Booker T won the WCW World Tag Team Championship for an eleventh time, this time with Test, and he also had a WWF Tag Team Championship reign with Test. At the Survivor Series, Booker T was eliminated third by The Rock after a roll-up and eventually The Alliance was defeated, causing them to disband.
In its aftermath, Booker remained a heel, and he joined forces with Vince McMahon and The Boss Man in December to feud with Stone Cold Steve Austin. After Booker T cost Austin a match against Chris Jericho for the WWF Undisputed Championship at Vengeance, Austin gained revenge by attacking Booker T in a "grocery store" by covering him in food.
Booker T's first WrestleMania appearance was at WrestleMania X8 against Edge. They feuded over who would appear in a fictional Japanese shampoo commercial. When the brand extension was introduced in March, Booker T was drafted to the Raw brand. Booker held the Hardcore Championship twice in May 2002, defeating Stevie Richards only to lose it to Crash Holly seconds later. He then re-defeated Crash and dropped the Belt to Stevie Richards a couple minutes later.
Goldust began trying to start a tag team with Booker, but Goldust kept costing Booker matches. With the nWo now operating in WWE, Booker T was eventually invited into the faction. His time there was short-lived, when he got (literally) kicked out of the group by Shawn Michaels, who believed Booker T was taking away from his own spotlight. Booker then turned face and found a partnership with Goldust and the pair teamed to battle the nWo. Booker and Goldust had a title shot against the The Un-Americans (Christian and Lance Storm) at SummerSlam, but The Un-Americans retained after interference from Test. At No Mercy, Booker and Goldust battled Chris Jericho and Christian for the tag titles, but they lost the match with Jericho using the title belt on Goldust.
He spent the rest of 2002 teaming with Goldust. They won the World Tag Team Championship at Armageddon in a Tag Team Elimination match defeating the teams of Christian & Chris Jericho, Lance Storm & William Regal, and the Dudley Boyz. They held the belts for about three weeks, when they lost them to Regal and Storm. Booker and Goldust lost the rematch and decided to go their separate ways. The gimmick for Booker and Goldust was Goldust being a strange, yet dependable ally who Booker eventually warmed up to after initial skepticism. By 2003, however, Booker T's popularity had soared and he amicably separated from Goldust, at Goldust's request, in order to pursue the World Heavyweight Championship. In February 2003, he eliminated The Rock to win a battle royal for the number one contendership, granting him a title shot at WrestleMania XIX.
Booker targeted Evolution after Batista and Randy Orton attacked Booker's former partner, Goldust. Several weeks before WrestleMania, the incumbent champion and Evolution's leader, Triple H, cut a controversial promo on Booker T. Triple H downplayed Booker T's WCW success, pointing out that the WCW Championship had been held by non-wrestlers like Vince Russo and actor David Arquette calling WCW and its title "a joke". He implied that Booker T, as a convicted criminal, would never win a world championship in WWE, although this is often misconstrued, as a racist promo, as he claimed "people like you" were not championship material. However this misunderstanding may have been intentional by Triple H knowing the heat he would generate. In the Wrestlemania XIX press conference Michael Cole questioned Triple H as to whether he had cut a racist promo, Triple H confirmed this was not the case and was indeed referring to Booker's criminal past. A week later, Booker got revenge by attacking Triple H in the bathroom, laying him out. Booker T lost to Triple H at WrestleMania XIX. For several weeks, he teamed with Shawn Michaels and Kevin Nash in a feud against Triple H, Ric Flair, and Chris Jericho. At Backlash, Booker's team lost when Triple H pinned Nash after a sledgehammer shot.
Afterward, Booker set his sights on the Intercontinental Championship. After losing a battle royal for the title at Judgment Day, Booker feuded with the champion Christian. After a few matches, Booker defeated him to become the new champion. About a month later, because of a nagging back injury, Booker lost the Intercontinental title back to Christian at an untelevised house show. Booker, meanwhile, was out of action until September.
When Booker returned in 2003, he announced he would be on Team Austin at the Survivor Series which would determine if Eric Bischoff or Steve Austin would be the General Manager of Raw. Booker's team lost the match, so Austin lost his position as Co-General Manager of Raw. Booker then entered a feud with Mark Henry, the man who eliminated him in the Survivor Series match. Booker defeated Henry at Armageddon.On the February 16, 2004 edition of Raw, Booker T and Rob Van Dam defeated Ric Flair and Batista for the World Tag Team Championship. Booker and Van Dam held the titles for a month, even defending the belts at WrestleMania XX in an 8-Man tag team match. They lost the belts eight days later on Raw back to Flair and Batista.On March 23, 2004 he was "traded" (along with the Dudley Boyz) to the SmackDown! brand in exchange for Triple H, but as part of a new storyline, he appeared unhappy with the move. Later on, Booker T bragged about how he was the biggest star on SmackDown! and turned heel when he began to feud with The Undertaker. Booker tried to utilize voodoo magic in order to try and overcome his "supernatural" foe; however, it did nothing to prevent him from losing to the Undertaker at Judgment Day.In mid-2004, Booker T set his sights on the United States Championship along with its champion, John Cena. After Cena got on the bad side of General Manager Kurt Angle, he did his best to get the title away from Cena. Cena successfully defended the title at The Great American Bash in a four-way elimination match against Booker, René Duprée, and Rob Van Dam. After General Manager Kurt Angle stripped Cena of his title, Booker took advantage of the situation and won an eight-man elimination match to become United States Champion. Booker and Cena participated in a best-of-five series of matches for the United States Championship. It culminated at No Mercy, where Cena won the title.
On October 21, SmackDown! General Manager Theodore Long placed Booker in a six man tag team match with Rob Van Dam and Rey Mysterio against John "Bradshaw" Layfield (JBL), René Duprée, and Kenzo Suzuki. JBL expected Booker to betray his partners, but instead Booker pinned him, thus turning face again. Booker T faced JBL for the WWE Championship at the Survivor Series on November 14, but lost after he was hit in the head with the championship belt. The next night, Booker T demanded a rematch, citing Orlando Jordan's interference. He was then joined by Eddie Guerrero and The Undertaker who also wanted a shot at JBL's title, prompting Theodore Long to make a Fatal Fourway match for the WWE Championship at Armageddon. Once again, Booker failed to win the title, as JBL retained it.
He then briefly teamed with Eddie Guerrero and feuded with Heidenreich. Booker won a 30-Man Battle Royal dark match at WrestleMania 21 last eliminating Raw's Viscera and "Masterpiece" Chris Masters. Subsequently, Booker was part of the tournament to name a new number one contender and made it to the Final Four. After Kurt Angle eliminated Booker, he returned the favor, costing Angle the match against JBL. The storyline then turned to a sexual nature, as Angle began stalking Booker's new wife, Sharmell. Booker defeated Angle at Judgment Day. On the May 26 edition of SmackDown!, Booker participated in a "Winners Choice" Battle Royal, with the winner choosing his opponent for the next week. Kurt Angle won and wanted to wrestle Sharmell. Booker protested, and the match was made into a Handicap match. Angle won by pinning Sharmell in a sexual position. The next week, Booker gained revenge on Angle, defeating him with a Scissors Kick.
On June 30, JBL defeated Christian, The Undertaker, Chris Benoit, and Booker T. During the match, Booker got specifically involved with Christian. Booker later defeated Christian at The Great American Bash. Booker T began teaming with Chris Benoit, eying the United States Championship again. Meanwhile, after a series of matches with MNM, Sharmell introduced some heelish characteristics unknown to Booker. Benoit was allowed to pick his next challenger to see who would face him at No Mercy, so Booker, Christian, and Orlando Jordan tried to impress Benoit by winning matches. He could not choose, so he made it a Fatal Four-way for No Mercy, where Benoit successfully defended his title. On the October 21 edition of SmackDown!, Booker T defeated Benoit for the United States Championship, due to an unseen assist from Sharmell. Theodore Long later showed footage of Sharmell interfering in Booker's matches. Later, Booker and Sharmell went to apologize to Benoit and give him a rematch, but instead, he attacked Benoit, and busted him open with the U.S. title officially turning heel once again. Booker then boasted that he had been fully aware of what Sharmell had been doing and had been playing dumb to fool everyone.On November 25, Booker T fought against Benoit for the United States Championship. The match ended when Benoit superplexed Booker and two referees made a three count on either competitor, claiming that their wrestler had won. Booker was stripped of the belt by Theodore Long, because of the confusion of who won since they pinned each other at the same time. Long decided to put Benoit and Booker against each other in a best of seven series, just as the two had in their WCW days. Booker took an early 3-0 lead. In a must win match during Armageddon, Benoit was able to defeat Booker T to bring the series to 3-1. At a house show on December 2, however, Booker was injured, and he did not wrestle again until after the "Best of Seven" series with Benoit was completed. Booker was scheduled to face Benoit in Match 5 of the Best of Seven Series at the SmackDown! tapings the following night. At the beginning of the show, General Manager Theodore Long said that Booker would have to forfeit. Both Booker and Benoit protested, with Benoit not wanting a cheap victory. Booker managed to persuade Long to allow him to choose a stand-in for the matches. Booker selected Randy Orton, over an unhappy Orlando Jordan, as his stand-in. Benoit was able to beat Orton in two matches. Orton, however, was able to defeat Benoit in the final match to win the series and the title for Booker T, who held the title until No Way Out where Benoit won it back.After losing the title, Booker was involved in a feud with The Boogeyman, who continually scared Booker and Sharmell over the next few weeks. The feud culminated in a match at WrestleMania 22 on April 2, where both Booker and Sharmell lost to the Boogeyman in a handicap match. The feud came to an end on the April 7 edition of SmackDown! where it was announced that Booker and his wife had taken out a restraining order on the Boogeyman.
Booker next entered the King of the Ring tournament on SmackDown!, advancing through to the finals due to a bye as his semi-final opponent, Kurt Angle, was unable to wrestle. The finals were held at Judgment Day where Booker defeated Bobby Lashley. Upon winning the King of the Ring tournament, Booker T changed his ring name to King Booker. Under this name, he went on to form "King Booker's Court", which included Queen Sharmell, William Regal, and Finlay. Over time, King Booker began to act as if he were a real king of "The SmackDown! Kingdom", including mannerisms and appearance of a typical English-style king, with the members of his court being real citizens of England and Ireland. His new persona included wearing a crown and speaking in a faux British accent, thus referring to himself as "Book-ah". This was intentionally broken whenever he was riled up, which always drove him to making a tirade in the former Booker T style. King Booker even went as far as having Lashley kiss his royal feet. As a result, Lashley defeated King Booker in a steel cage match to retain the United States title.
King Booker won a #1 Contenders battle royal to win a World title shot at The Great American Bash. Booker won the World Heavyweight Championship from Rey Mysterio at the event, after Chavo Guerrero hit Mysterio with a steel chair. This win caused him to proclaim himself as the "King of the World".
In spite of the break-up of his Court, King Booker defeated Batista on the October 20 edition on SmackDown, due to interference from WWE Champion John Cena and then ECW World Champion Big Show. At Cyber Sunday, King Booker retained his World Heavyweight Championship after Kevin Federline interfered and hit John Cena with the World title belt. King Booker became the "Champion of Champions" in a match that marked the first time in which the World Champions from Raw, SmackDown, and ECW fought against each other. Booker lost the World Heavyweight Championship to Batista on November 26 at Survivor Series. After losing the World title, Booker then feuded alongside former royal court member Finlay against Batista and John Cena, which led up to Armageddon where they lost. While competing in the Royal Rumble match, Booker was eliminated by Kane. A frustrated Booker then returned to the ring illegally and eliminated Kane. This started a short feud between the two resulting in a match at No Way Out, which Kane won. King Booker then won a Money in the Bank qualifying match, defeating Kane (with assistance from The Great Khali) and earned himself a spot in the match at WrestleMania 23. At WrestleMania, Matt Hardy set up Sharmell for a Twist of Fate during the Money in the Bank match with the briefcase in King Booker's grasp - thus forcing him to choose between a guaranteed title shot and his wife. He chose to defend his Queen and lost the match. On the April 6 edition of SmackDown!, Booker attempted to take revenge. However, he lost the match against Matt Hardy, and Sharmell declared her disappointment in him and slapped him. In an attempt to impress his Queen, King Booker then attacked The Undertaker but was Tombstoned on an announce table. Booker was then taken off television to deal with a knee injury.
On the June 11 edition of Raw, King Booker (along with Queen Sharmell) was drafted from SmackDown! to Raw as part of the WWE Draft. On July 16, King Booker came to the ring using Triple H's theme music "The King of Kings", even using his video. King Booker then declared that neither Triple H nor Jerry Lawler could be known as "The King". Booker then began a feud with Lawler, defeating him on the August 6 edition of Raw where the loser had to crown the winner the next week. When the time came, Lawler refused, declaring that Triple H was still a king and announcing that King Booker would battle Triple H at SummerSlam. Booker then attacked Lawler, throwing him into the ring post and hitting him with a TV monitor. At SummerSlam, Booker lost to the returning Triple H. On the August 27 edition of Raw, Booker had his last match in the WWE against WWE Champion John Cena in a non-title match which he lost by disqualification when Randy Orton interfered.
In August, he was linked to Signature Pharmacy, a company thought to be distributing performance enhancing drugs. He was then suspended by WWE for violating its Wellness Policy. He denied using any drugs and being a customer of Signature Pharmacy. In October 2007, Booker T requested his and Sharmell's release from their WWE contracts, to which the WWE granted.