Sabu was included in the WWF invasion angle in 2001, in which wrestlers invaded WWF's Monday Night Raw program and held hardcore-style matches and angles on the show. One memorable moment occurred at this show when Sabu appeared during a match and prepared for an aerial move off the "R" in the "RAW" lettered entryway onto Team Taz members, but accidentally fell off the "R".
On April 24, 2006, Sabu's official website reported that he signed a one-year contract with World Wrestling Entertainment. At the One Night Stand pay-per-view, Sabu faced Rey Mysterio for the World Heavyweight Championship. At the end of the match, Mysterio found himself standing on a ringside table with Sabu flying at him. Sabu caught the champ in a front facelock and nailed him with a DDT which caused both men to crash through the table. At this point, the WWE medical staff rushed to the injured men and declared neither man could continue and ordered the match stopped, resulting in a No Contest in which Mysterio kept his title.
On the June 13 premiere of ECW on Sci Fi, Sabu won a 10 man Extreme Battle Royal with the stipulation that the winner face John Cena at Vengeance. Sabu further fueled the feud during the next week's Raw, when he interfered in a Cena match and performed a Triple Jump Leg Drop on him, diving onto Cena and putting him through the announcers' table. Cena defeated Sabu in their "Extreme Lumberjack match" at Vengeance. On July 2, Sabu, traveling with fellow ECW wrestler Rob Van Dam, was arrested and charged with possession of drug paraphernalia, and nine Vicodin tablets following a traffic stop in Hanging Rock, Ohio following a house show in Huntington, WV. Sabu was fined $1,000 based on the guidelines of WWE's Wellness Policy. Meanwhile, he defeated Stevie Richards in an Extreme Rules match at Saturday Night's Main Event.
Towards the end of July, Sabu began to talk on camera for himself - instead of using a go between - and demanded a shot at The Big Show's ECW World Championship which Paul Heyman refused to grant him in order to "protect" his champion. Instead he forced him into a match against the returning Kurt Angle to determine a number one contender. When that match was interrupted by the returning Rob Van Dam another match was signed, Angle versus Van Dam versus Sabu, for the number one contendership (Angle then became too injured to compete and was pulled from the match). Sabu beat Rob Van Dam in their ladder match to win a shot at Big Show at SummerSlam, a match which he ended up losing. After SummerSlam, he became a main eventer at ECW, with the majority of the matches being Extreme Rules. He also started to form tag teams with the likes of Rob Van Dam and The Sandman to face Test, The Big Show, Paul Heyman and his ally Matt Striker.
At Survivor Series, Sabu teamed up with John Cena, Bobby Lashley, Rob Van Dam and Kane to face the team of The Big Show, Test, Montel Vontavious Porter, Finlay and Umaga. Sabu eliminated Test following a Tornado DDT, but he was later eliminated by Big Show via pinfall after receiving a chokeslam. In the end, Team Cena gained victory. At December to Dismember Sabu was originally set to appear in the main event, an extreme elimination chamber match against The Big Show, Test, Rob Van Dam, CM Punk and Bobby Lashley, but was "taken out" and replaced by Hardcore Holly. The following episode on ECW, CM Punk and Rob Van Dam got on the mic before their match with Test and Hardcore Holly and dedicated the match to Sabu. When Punk and Van Dam won the match, Paul Heyman and his security team came out and had beaten down on the two. Sabu later made his return with a heavily wrapped arm to make the save. Sabu made his Royal Rumble debut in the 2007 Royal Rumble where he was eliminated by Kane after receiving a chokeslam over the top rope and through a table.
Sabu joined the ECW Originals along with Rob Van Dam, Tommy Dreamer and The Sandman. The ECW Originals began a feud with the New Breed (Elijah Burke, Kevin Thorn, Marcus Cor Von and Matt Striker). The two teams faced off in a match at WrestleMania 23 in which the ECW Originals won. The ECW after that, there was an ECW Extreme Rules match between the New Breed and the ECW Originals, which the New Breed won after Elijah Burke performed the Elijah Express on Sabu through a table. On May 16, 2007 Sabu was released from his WWE contract.