He was introduced to WWF audiences on the July 9, 2001 episode of Raw as a member of the Alliance during the Invasion angle. When the angle ended in November, He disappeared from television.
He was brought back to the main roster of the now renamed World Wrestling Entertainment in April and placed on the Raw "brand". There, he turned face and was given a gimmick that saw him proclaim that he was "Just a Regular Guy", for which he was featured in vignettes and backstage segments showing him in normal situations that were then augmented by "disgusting" antics such as brushing his teeth and his dogs teeth with the same brush and eating food from the floor. However, this angle was short-lived. He soon reverted back to his "Innovator of Violence" gimmick and amassed fourteen reigns as Hardcore Champion. During this time, he was the final person to hold it before it became unified with the Intercontinental Championship in a match with Rob Van Dam. After losing the Hardcore Championship, Dreamer jumped into a feud with Raven, defeating him in a Loser Leaves Raw match on June 24 to send him to Raw's sister show, Heat. As 2003 and 2004 went on, Dreamer was used less and less on WWE television.
In 2005, Dreamer was a major part of the ECW One Night Stand "reunion show" pay-per-view held under the World Wrestling Entertainment banner. He, along with a number of extreme superstars, took part in promotional hype for the event on episodes of Raw and, with The Sandman, he wrestled the Dudley Boyz in the main event. For the 2006 event, he was placed into an angle that had him and Terry Funk at odds with then-heels, Mick Foley and Edge over the meanings of "extreme". The angle ended with a six-person-intergender-tag team match at the pay-per-view where Dreamer, Funk, and Beulah McGillicutty lost to Edge, Foley, and Lita.
When the ECW brand officially launched on the Sci Fi channel, Dreamer and the Sandman were put into one of the brands first feuds, an "old school versus new school" feud, against Test and Mike Knox. In November and December he engaged in a short feud with Daivari and The Great Khali, but Khali was sent to the Raw brand before it could come to a conclusion. Not long after Khali left ECW, The New Breed stable was established, consisting of wrestlers new to ECW: Elijah Burke, Marcus Cor Von, Matt Striker and Kevin Thorn. In response, a stable of ECW Originals was created, and the teams continued to clash in singles and tag matches, trading wins on the weekly ECW show throughout the spring of 2007. The Originals won a standard-rules four-on-four match at WrestleMania 23, but lost an extreme-rules rematch on the next Tuesday's show. The feud continued until a number of roster moves left the Originals nearly barren.
In late 2007, Dreamer took part in the ECW brand's elimination chase to name a number one contender to the ECW Championship. During the series of matches, also involving Stevie Richards, Elijah Burke, and Kevin Thorn he added a bandana, worn on his head, to his ring gear. Dreamer emerged victorious in the final match against Burke, only to be surprised by ECW's General Manager Armando Estrada forcing him to face Big Daddy V, who promptly beat him for the number one contendership.
In the beginning of 2008, Dreamer was paired with ECW brand enhancement talent Colin Delaney as a sort of mentor after Delaney was consistently and easily defeated on the weekly ECW television show. They challenged The Miz and John Morrison for the WWE Tag Team Championship after they defeated them in a non-title match, but they lost the title match in an Extreme rules match. At WrestleMania, he participated in a 24-man battle royal to earn an opportunity for the ECW Championship later in the event, but failed to win. On the 100th episode of ECW, Dreamer was defeated in an extreme rules match by Mike Knox. He participated in a Singapore cane match at One Night Stand, but failed to win. At The Great American Bash on July 20, 2008, Delaney turned on Dreamer, costing him his ECW Championship match against Mark Henry. He defeated Delaney in an extreme rules match. After that, Dreamer started a feud with the new superstar Jack Swagger. They faced in a classic wrestling match, but Dreamer lost the match after he used his DDT on Swagger. Then Swagger defeated Dreamer in an Extreme rules match, ending the feud.
On the January 13, 2009 episode of ECW, Dreamer announced that if he failed to win the ECW Championship by June 6, when his WWE contract was to expire, he would no longer wrestle for ECW. The storyline saw Dreamer start a losing streak that ended when he defeated Paul Burchill on the February 24 edition of ECW. On the April 28 edition, Dreamer received a match for the ECW Championship against then-champion Christian, which went to a no-contest when Jack Swagger interfered. Dreamer was granted a one-day extension on his contract, allowing him one last chance at the ECW Championship, challenging the champion Christian and Jack Swagger in a triple threat match at Extreme Rules. At Extreme Rules, Dreamer pinned Jack Swagger in a hardcore triple threat match, capturing the ECW Championship.
After successful title defenses, one against Christian and also a Championship Scramble match at The Bash, Dreamer eventually lost the championship back to Christian at Night of Champions. On the July 28 episode of ECW, Dreamer announced he would exercise his rematch clause against Christian the following week. The two faced off in an Extreme Rules match, in which Christian retained the championship.
After his championship pursuit had ceased, Dreamer began teaming up with Christian, Yoshi Tatsu and Goldust on various occasions to take on William Regal and his allies Vladimir Kozlov and Ezekiel Jackson, exchanging victories and losses. On the December 29 episode of ECW, Dreamer wrestled Zack Ryder and lost. If Dreamer was to lose the match then he would be (kayfabe) forced to retire from in-ring competition. After the match, Dreamer made a farewell speech in which he thanked the fans before exiting the ring with his two daughters. A few days later on January 4, 2010, Dreamer was officially released by WWE.
On December 17, Dreamer made one-night return to WWE during the annual Slammy Awards show, as the mystery tag team partner of The Miz & Alberto Del Rio in a match against Three Man Band members, Heath Slater, Drew McIntyre and Jinder Mahal. Later that night, Dreamer was attacked backstage by The Shield.
On April 6, 2013 Dreamer was backstage at the WWE Hall Of Fame Induction ceremony, meeting up with fellow ECW veterans Rob Van Dam, Joey Styles and Paul Heyman.
On the May 17, 2015, NXT live event in Philadelphia, Pennsylvania, Dreamer would face Baron Corbin in a losing effort. On the November 30, 2015 episode of Raw, Dreamer would make a special appearance, teaming with The Dudley Boyz in a six-man tag match against The Wyatt Family, with the match ending in a no contest. The following week on Raw, Dreamer and the Dudley Boyz would be joined with Rhyno, forming Team Extreme, where they competed in a 16-man Elimination Fatal 4-Way Tag Team match, with Team Extreme eliminating the Wyatt Family before they would be eliminated by The League of Nations. Later that night, Dreamer would be defeated by Braun Strowman. At TLC: Tables, Ladders and Chairs (2015), Team Extreme were defeated by The Wyatt Family (Bray Wyatt, Luke Harper, Erick Rowan and Braun Strowman) in a elimination tables match. On the December 14 edition of Raw, The ECW Originals were defeated yet again by The Wyatt Family in an Extreme Rules match.