In the weeks leading up to the Royal Rumble, Vader's debut was heavily hyped on TV as he was billed as "The Man They Call Vader". He made his first World Wrestling Federation appearance as a participant in the Rumble match. He entered at number 13 and eliminated Jake Roberts, Doug Gilbert, one member of the Swat Team, and Savio Vega. He also fought with his ally Yokozuna. Vader was eliminated by Shawn Michaels before he reentered the ring and started assaulting everyone, including Michaels. Vader defeated Vega on the following Monday Night Raw, before assaulting WWF officials. Eventually, WWF President Gorilla Monsoon demanded that Vader cease his attacks, and received a Vader bomb for his efforts. In the storyline, Vader was suspended for his actions (in reality, he needed time off for shoulder surgery).
Jim Cornette campaigned for Vader's reinstatement, and by the time Vader returned, Yokozuna had left Cornette's management. At February's In Your House 6, Vader appeared during Yokozuna's match against The British Bulldog. Yokozuna was about to pin The Bulldog, when Vader attacked him, handcuffed him, and delivered a severe beating. This led to what was supposed to be a one-on-one encounter between Vader and Yokozuna at WrestleMania XII. However, the match became a six-man tag team match pitting Vader, Owen Hart, and The British Bulldog against Yokozuna, Ahmed Johnson, and Jake Roberts. The stipulation was that if Yokozuna's team won the match, he would have five minutes alone with Cornette in the ring; this never occurred as Vader's team won the match when Vader pinned Roberts.
Vader then attacked WWF Champion Shawn Michaels after one of Michaels's matches. Vader's attack on Michaels earned him a spot in a six-man tag team match at In Your House 9: International Incident. Vader, Owen Hart, and The British Bulldog teamed up against Michaels, Ahmed Johnson, and Sycho Sid. Vader pinned Michaels to win the match for his team. Vader faced Michaels again at SummerSlam, where Vader won by count-out. Cornette, however, realized that the title could not change hands through a count-out and got the match restarted. This time, Michaels used Cornette's tennis racket and was disqualified. Again, Cornette managed to get the match started over. Finally, Michaels scored a pinfall over Vader.
Following his feud with Michaels, Vader faced off against The Undertaker in a singles match at the Royal Rumble. During the match, The Undertaker's former manager, Paul Bearer, attacked him and helped Vader win; Bearer then became Vader's manager. Both Vader and Undertaker went on to compete in the Royal Rumble match, during which Steve Austin was eliminated by Bret Hart. However the referees did not see this, as they were attending to Terry Funk and Mankind on the floor, allowing Austin to sneak back into the ring and eliminate both Vader and Undertaker, then Bret Hart, who was busy eliminating Fake Diesel, and win the Rumble. As a result of this, Vader and the other men eliminated Austin, Bret Hart and The Undertaker, were put into the four-way main event of February's In Your House 13: Final Four for the WWF Championship. Vader, after bleeding profusely, was eliminated by The Undertaker. Bearer then persuaded his two proteges, Vader and Mankind, to go after the Tag Team Championship, despite the fact that the two men often brawled between themselves. They failed in their bid to win the tag team gold at WrestleMania 13.
Vader again received an opportunity to face The Undertaker (this time for the WWF Championship) at In Your House 16: Canadian Stampede, but lost. On the following night's Raw is War, Vader wrestled The Patriot. The Patriot won the match and then went after Bret Hart, who came to ringside during the match. Vader attacked The Patriot, and then brought him back into the ring, where he went for the Vader Bomb. Hart came into the ring and laid the Canadian flag over The Patriot. Vader got down, picked up the Canadian flag, broke it, and started a brawl with Hart. This turned Vader face and served to bring Vader into the USA vs. Canada feud. At Survivor Series, Vader was the leader of Team USA, with Goldust, Marc Mero, and Steve Blackman (replacing the injured Patriot) as they faced Team Canada, composed of The British Bulldog, Jim Neidhart, Doug Furnas, and Phil LaFon. During the match, Goldust walked out on his team. Team USA lost the match after The Bulldog pinned Vader after hitting him with the ring bell. Goldust and Vader feuded throughout the fall and finally faced off at the Royal Rumble, in a match which Vader won. Goldust eliminated Vader from the Royal Rumble match later that night (Vader entered at number 30).
Kane and Vader had their first in-ring meeting at No Way Out of Texas. Vader lost after a chokeslam and Tombstone piledriver by Kane and was subsequently attacked by Kane with a large steel wrench. Vader was taken away on a stretcher and was kept off of TV for a while. At Unforgiven, a few months later, Vader returned during Kane's Inferno match against The Undertaker. Kane was attempting to leave the match when Vader appeared and fought him back to the ring to continue the match, which Kane lost. Vader and Kane had a rematch at Over the Edge in a Mask vs. Mask match. Vader attempted to use a wrench on Kane (like the one used on him months before), but Kane picked up the victory and Vader lost his mask. In a post-match interview with Michael Cole, Vader said, "I made the biggest mistake of my life. Maybe Vader time is over. I'm a piece of trash. A big fat piece of trash."
Subsequently, Vader had a series of losses and was reduced to the status of a jobber, having a feud with Mark Henry which Vader lost. After considering retirement, Vader instead negotiated his own release from the WWF so he could once again wrestle in Japan. His final WWF pay-per-view match was a loss to Bradshaw at Breakdown: In Your House in a No Holds Barred match on September 27. He lost to Edge on Sunday Night Heat in his final televised WWF match. His last match in a WWF ring was on October 25 at a Madison Square Garden house show in a Triple Threat Match with Mankind and Ken Shamrock, which Vader was defeated after he tapped out to Shamrock's Ankle Lock.