In 1999, Moore was hired by World Championship Wrestling (WCW), where he was placed in a faction known as 3 Count. 3 Count, which consisted of Moore, Evan Karagias and Shane Helms, was a trio of young male wrestlers who utilized a boy band gimmick. 3 Count debuted in WCW in November 1999, and they began lip-syncing the song "Can't Get You Out Of My Heart" in the ring before their matches. On the February 28, 2000 episode of WCW Monday Nitro in Minneapolis, Minnesota, all three members of 3 Count defeated Brian Knobbs to win the WCW Hardcore Championship with all three members of the team simultaneously pinning him. 3 Count reigned as "co-champions" until March 19, at Uncensored, where Knobbs regained the title by pinning all three men consecutively.
When the team reconvened after Helms received a broken nose late in the summer of 2000, they began performing a new song, "Dance With 3 Count". In storyline, Tank Abbott became an avid fan of 3 Count, and he began protecting them during their performances, attacking anyone who disrupted them, eventually acting as their talent manager and occasional inserting himself as a back-up dancer. 3 Count were involved with a long-running feud with The Jung Dragons, with the Dragons attempting to steal 3 Count's fictional recording contract. This led to a ladder match between the two teams at New Blood Rising, which 3 Count won due to Abbott's interference. As a result, Abbott claimed that he should be the lead singer of 3 Count, and was kicked out by the other three members, leading to a feud. Following this, 3 Count briefly feuded with Misfits in Action.
In late 2000, 3 Count began to fall apart, with Moore and Helms kicking Karagias out of the group for continually stealing the spotlight. Karagias joined forces with former Jung Dragons member Jamie Knoble and the three teams met in a triangle match at Mayhem, which 3 Count won. At Starrcade, the six men faced off in a ladder match for the number contendership to the WCW Cruiserweight Championship. Both Moore and Helms grabbed the contract at the same time, and later wrestled for the opportunity to face the champion, which Helms won.
Moore and Helms both participated in a cruiserweight elimination match at SuperBrawl Revenge on February 18, in which Helms eliminated Moore and went on to win the match. Following the match, Moore and former partner Karagias attacked Helms. Moore and Karagias joined forces once again to take part in a tournament for the WCW Cruiserweight Tag Team Championship, but were eliminated by Billy Kidman and Rey Mysterio, Jr.. In March 2001, the World Wrestling Federation purchased WCW, which included Moore's contract.
In July 2002, Moore was assigned to the SmackDown! brand, initially appearing on Velocity. In December, Moore became a heel acolyte of Matt Hardy, who had begun proselytizing a philosophy known as "Mattitude" and calling himself "Matt Hardy Version 1.0". Moore became a "Mattitude Follower" (abbreviated "MF'er") and started dressing like Hardy, accompanying him to ringside and interfering in his matches. Moore helped Hardy to lose several pounds in order to qualify for a WWE Cruiserweight Championship match at No Way Out. During the championship match, Moore distracted champion Billy Kidman to enable Hardy to get the win and the championship. On April 24, 2003, Crash Holly was revealed as the newest MF'er. He was subordinate to Moore and, as such, was referred to as a "Moore-on". When Hardy was displeased with either Moore or Holly, he would physically attack them. Holly was later released from WWE on June 30. On September 23, Moore and Hardy challenged Los Guerreros for the WWE Tag Team Championship, but were unsuccessful.
Moore and Hardy continued to work together until November 17, when Hardy left SmackDown! and joined the Raw brand. As a result, Paul Heyman, SmackDown!'s then-general manager, decided to punish Hardy vicariously for leaving his show by forcing Moore to face a series of much larger opponents. In successive weeks, Moore was squashed by Matt Morgan, Nathan Jones, and The Big Show before unexpectedly defeating A-Train in an upset on the December 11 episode of SmackDown!. The following week, WWE Champion Brock Lesnar was scheduled to defend the championship against a wrestler chosen by a lottery machine, which produced Moore's name. After defeating Moore, Lesnar revealed that the process had been rigged, and Moore's name was on all the balls. Immediately afterward, Moore teamed with Hardcore Holly to defeat A-Train and Morgan, earning Holly a championship match against Lesnar. In 2004, at WrestleMania XX, Moore took part in a "Cruiserweight Open" for the Cruiserweight Championship, but was eliminated by Último Dragón. His next high profile appearance was on the July 8 episode of SmackDown!, which saw Moore wrestle under a mask as "El Gran Luchadore" to face John "Bradshaw" Layfield (JBL) in the match for the WWE Championship. Initially Moore was dominated by his much larger opponent, but a second Luchadore (the disguised Eddie Guerrero) took Moore's place, prompting Layfield to run away and giving Moore the victory by countout. For the remainder of 2004 and early 2005, Moore competed in the cruiserweight division and on Velocity. Moore received a WWE Championship match on the December 30, 2004 episode of SmackDown, but was quickly defeated by JBL. Moore appeared at the No Way Out pay-per-view in February 2005, competing in a gauntlet match for the Cruiserweight Championship, but was eliminated by Paul London.
On March 21, 2005, he suffered a concussion. He quickly recovered from his injuries, but was released by WWE on July 5.
On March 17, 2006, WWE released an interview with Moore talking about his imminent return to the company. In July 2006, Moore began appearing as part of WWE's ECW brand, making his first appearances in vignettes calling himself "The Reject". His in-ring debut was a loss to CM Punk on September 12, a week before Punk had confronted Moore and called him a "poser" before slapping him. After one more loss to Punk, Moore made only sporadic appearances throughout the rest of 2006 and early 2007, losing each time.
On the February 16, 2007 episode of SmackDown!, Moore suddenly switched brands, appearing in an in-ring brawl with other SmackDown! cruiserweights, which was a prelude to a Cruiserweight Open at No Way Out. Moore was eliminated from the Cruiserweight Open by the defending WWE Cruiserweight Champion Gregory Helms. Moore then established himself as a fan favorite by teaming with Scotty 2 Hotty and Jimmy Wang Yang to defeat Helms, Chavo Guerrero, and Daivari in a six-man tag team match.
Following a hiatus from television, Moore returned on the June 15 episode of SmackDown!, competing in a fatal four-way number one contender match for the Cruiserweight Championship, which was won by Wang Yang and also involved Daivari and Jamie Noble. The following week, Moore teamed with Wang Yang in a losing effort against Guerrero and Noble. Moore competed in the 20-man battle royal for the World Heavyweight Championship in July, but was the third person to be eliminated. He also competed in the "Cruiserweight Open" at The Great American Bash along with Noble, Funaki, Wang Yang, and Guerrero. The match was inadvertently won by Hornswoggle. He also faced Noble and Guerrero, in losing efforts. Moore began feuding with Noble, appearing in several backstage vignettes together, where he mocked Noble for his obsession with Hornswoggle. Moore defeated Noble on the September 14 episode of SmackDown!, by pretending that Hornswoggle was at ringside, distracting Noble and allowing Moore to pin him for the victory. In a rematch two weeks later, Noble pinned Moore.
In October 2007, Moore formed a tag team with Yang, with the two defeating Deuce 'n' Domino. They later competed in a tag team battle royal to determine the number one contenders to the WWE Tag Team Championship on the November 9 episode of SmackDown, but were the second team eliminated. In December, Moore and Yang challenged John Morrison and The Miz for the WWE Tag Team Championship, but were unsuccessful, igniting a feud between the two teams. The following week on ECW, Moore and Yang defeated Morrison and The Miz in a non-title match, to earn a rematch for the championship. On January 1, 2008, Moore and Wang Yang once again beat Morrison and the Miz, this time in a six-person tag team match also involving Layla and Kelly Kelly. The following week, in a "Fifteen Minutes of Fame" match, Moore and Wang Yang tied the champions on pinfalls, meaning Miz and Morrison retained the championship. Throughout late January and February, Moore and Yang moved into a feud with Deuce 'n' Domino, defeating them two weeks in a row. On the February 15 episode of SmackDown, Moore, Yang, and Jesse and Festus defeated Deuce 'n' Domino and Curt Hawkins and Zack Ryder in an eight-man tag team match on SmackDown. In April, Moore and Yang reignited their feud with Morrison and The Miz, losing to them twice in tag team encounters. Yang and Moore went on to win singles matches against Morrison and The Miz respectively, earning another match for the WWE Tag Team Championship on the May 2 episode of SmackDown, but were unsuccessful once again.
After this feud ended, Moore was rarely utilized. On August 8, 2008, WWE announced that Moore had been released from his WWE contract.