On the April 14, 2003, episode of World Wrestling Entertainment (WWE)'s Raw, one of WWE's primary television programs, Joey Mercury (as Joey Matthews) and Christian York teamed up to defeat Phil Brown and Pat Cusick in a dark match. His early months in WWE saw him taking on Lance Storm and Crowbar in dark matches, and Matt Hardy, Último Dragón and A-Train on Velocity. He also lost to Rhyno and Maven on Sunday Night Heat.
In his (and Johnny Nitro's) 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, attacking him and breaking up the group. Later that night Nitro and Melina 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. 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.
In 2010, Mercury returned to WWE at the SmackDown tapings on April 20, where he lost to Shelton Benjamin in a dark match. On April 25 at Extreme Rules, he reappeared on TV as a masked member of CM Punk's Straight Edge Society and interfered in Punk's match with Rey Mysterio, helping him pick up the win. Mercury would continue to interfere in Punk's matches for the following months, before being unmasked by Big Show on the July 23 episode of SmackDown. At SummerSlam, Mercury's name was tweaked to Joseph Mercury. In early September it was reported that Mercury had undergone surgery on a torn pectoral muscle. He never made it back to TV, as the Society was broken up by the time he had healed. He later began working as a trainer in NXT Wrestling, a WWE developmental territory. After a long hiatus from TV, Mercury appeared on the October 7 edition of Raw to assist Triple H after The Big Show attacked him.
He was in a promo backstage on the July 21st, 2014 edition of Raw talking with Triple H about who will face John Cena at SummerSlam. Starting in mid-2014, Mercury began to make occasional on-screen appearances as part of The Authority, along with Jamie Noble. The pair were frequently used as henchmen, performing various tasks for Triple H. On the November 24, 2014, edition of Raw, J&J Security wrestled the first televised matches for each man in several years, partnering with Rollins in a three-on-two handicap match against John Cena and Dolph Ziggler, which they lost despite the odds being on their side. On December 29, 2014 the guest general managers of Raw, Christian and Edge hosted Seth Rollins as the special guest on their talk show. Rollins however took out Christian with the help of Big Show and J&J Security and punced on Edge's injured neck. Rollins threatened that if Cena didn't bring back The Authority he would hit Edge with a Curb Stomp which would snap his neck since he had to retire because any further damage could cause him to become paralysed or worse. Cena, in order to save Edge, brought The Authority back to power. On the February 5, 2015 episode of SmackDown, J&J Security once again teamed with Rollins in a 3-on-1 Handicap match against Daniel Bryan in a losing effort. On the March 16 episode of Raw, both Mercury and Noble left the Authority due to Rollins not listening to them. Later that night, it was revealed to be a ruse, with all the Authority members coming out to help Rollins take out Randy Orton, but they were stopped when Sting made a surprise appearance and helped Orton fight off the Authority.
On the June 8, 2015 episode of Raw, J&J Security stood up to Rollins, turning face in the process. Later that night, they defeated Rollins in a handicap match due to interference from Dean Ambrose. On the June 22 episode of Raw, J&J Security reconciled with Rollins when the three of them and Kane attacked Brock Lesnar, turning heel once again. On the July 6 episode of Raw, Mercury was viciously beaten by Lesnar, who after destroying his and fellow J&J Security member Jamie Noble's Cadillac, which had been gifted to them by WWE World Heavyweight Champion Seth Rollins the week before, picked him up and tossed him onto the then unbroken windshield of it.
On July 7, it was reported that Mercury suffered mild contusions as a result of the attack and Both members of J&J Security would be out of action indefinitely.
After sitting out the rest of the year, both Noble and Mercury appeared on the March 14, 2016 Raw by breaking up the brawl between Triple H and Roman Reigns.