In late 2000, Mercury, as Joey Matthews, and along with Christian York, joined Extreme Championship Wrestling (ECW), and lost to Danny Doring and Roadkill at Anarchy Rulz. They then began a feud with Simon and Swinger, whom they lost to at November to Remember, but defeated at Massacre on 34th Street. They competed in ECW for approximately six months, until the promotion closed in January 2001 and were on the company's final pay-per-view Guilty as Charged, where they suffered a loss to Jerry Lynn and Cyrus.
On the April 14, 2003 episode of World Wrestling Entertainment (WWE)'s Raw, one of WWE's primary television programs, Matthews and York teamed up to defeat Phil Brown and Pat Cusick in a dark match. The following months in WWE saw him taking on Lance Storm and Crowbar in dark matches, and Matt Hardy, Último Dragón and A-Train on Velocity.
In 2005, Matthews officially debuted in WWE under the name Joey Mercury, where he formed a team with Johnny Nitro and their valet Melina, in which they were called MNM. In their first match for the SmackDown 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 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 titles 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 on 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 and orbital bone. He immediately left the match and was rushed to an emergency room where he received more than thirty stitches. 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 television as a masked member of CM Punk's Straight Edge Society stable and interfered in Punk's match with Rey Mysterio, helping him pick up the win. Mercury continued to interfere in Punk's matches during the following months, before being unmasked by Big Show on the July 23 episode of SmackDown. This led to a handicap match at SummerSlam, where Big Show defeated the entire Society. In early September, it was reported that Mercury had undergone surgery on a torn pectoral muscle.
On the September 29, 2014 episode of Raw, Mercury and fellow producer Jamie Noble aligned themselves with The Authority. Dubbed J&J Security, Mercury and Noble began acting as bodyguards to Authority member Seth Rollins. On the November 24 episode 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. On the March 16, 2015 episode of Raw, both Mercury and Noble seemingly left The Authority due to Rollins not listening 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 by Sting, who made a surprise appearance and helped Orton fight off The Authority. On the June 22 episode of Raw, J&J Security reconciled with Rollins when the three of them and Kane attacked Brock Lesnar. 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 prized Cadillac car, which had been gifted to them by 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.
Mercury appeared on the March 14, 2016 episode of Raw breaking up the brawl between Triple H and Roman Reigns. In January 2017, it was reported that Mercury had been released from WWE.