In their first match for the brand, in April 2005, they won the WWE Tag Team Championship from Rey Mysterio and Eddie Guerrero. They held the titles for three months, having successful titles defenses against the teams of Mysterio and Guerrero and Hardcore Holly and Charlie Haas, before dropping them to the new Legion of Doom (LOD) at The Great American Bash in July 2005. They recaptured the titles in a four-way match defeating The Mexicools, William Regal and Paul Burchill, and LOD, but lost them to Mysterio and Batista days before the Armageddon pay-per-view in December. Due to help from Mark Henry, they defeated Mysterio and Batista in a rematch on December 30 to win the Championship for the third time.
They began a rivalry with the team of Paul London and Brian Kendrick that lasted over three months, until the Judgment Day pay-per-view on May 21, 2006, where MNM lost the tag team title to London and Kendrick. Nitro and Melina suddenly turned on Mercury, breaking up the group. Later that night they were fired from the SmackDown! brand in storyline, to facilitate their move to Raw, where they reappeared the following week. The legitimate reason for the team's sudden split was later revealed to be Mercury failing a WWE Wellness Policy drug test and being forced to serve a 30 day suspension.
Mercury stayed off WWE television for six months. During that time, he went through a drug rehabilitation in College Park, Georgia at a facility that has an exclusive contract with the WWE. Afterwards, he was sent back to OVW. Mercury made a surprise return on the November 27, 2006 episode of Raw, temporarily reforming MNM with Nitro and Melina to take up the also recently reunited Hardys (Matt and Jeff) "open challenge" for ECW December to Dismember.
The Hardys went on to win the match, but the feud continued across all three brands (Raw, ECW, and SmackDown!), and in a fatal-four way ladder match at December's Armageddon event, also involving London and Kendrick, and Dave Taylor and William Regal, Mercury suffered a legitimate injury when he was struck in the face with a ladder, breaking his nose. He immediately left the match and was rushed to an emergency room where he received five stitches to the inside of his nose and fifteen to the outside. As a result, Nitro continued the match on his own.
After missing a few weeks, Mercury returned wearing a protective face mask and his injury was worked into the angle, with both he and Nitro attempting to injure the Hardys in various ways for revenge. MNM lost to The Hardys at the Royal Rumble, and again at the No Way Out pay-per-view in February which concluded the feud. He also wrestled in singles competition on SmackDown! until he was released from his WWE contract on March 26, 2007.