Orndorff signed with the World Wrestling Federation in late 1983. Starting in January 1984, Orndorff took on "Rowdy" Roddy Piper as his manager. Piper nicknamed Paul Orndorff “Mr. Wonderful," a nickname that he has used ever since. Orndorff made his WWF debut against Salvatore Bellomo on the night that Hulk Hogan defeated The Iron Sheik for the WWF World Heavyweight Title and "Hulkamania was born", January 23, 1984 in Madison Square Garden. Orndorff became one of the first people to challenge for the world title, shooting straight to the main event less than a month after his debut. Hogan disposed of the challenger and moved on while Orndorff fought a variety of opponents including the Intercontinental Champion Tito Santana. When Piper assaulted Jimmy Snuka on the set of Piper's Pit, Orndorff (as well as Bob Orton, Jr.) assisted the Rowdy One in his fights. Orndorff and Piper often faced Snuka and "The Tonga Kid" in tag team competition.
Near the end of 1984, Roddy Piper’s assault on Cyndi Lauper brought Orndorff and Piper on a collision course with Hulk Hogan and Mr. T. Hogan’s feud with Piper also meant that Orndorff was thrust back into the main event picture; he defeated Tony Atlas at The War to Settle the Score and then played a part in the main event. The fallout from The War to Settle the Score led to the creation of WrestleMania, with Hogan and Mr. T (backed by Jimmy Snuka) taking on "Rowdy" Roddy Piper and Paul Orndorff in the main event. Orton's interference at the end of the match backfired when he accidentally hit Orndorff with the cast on his arm, allowing Hogan to pin Orndorff and win the match for his team. Blaming Orndorff for the loss, Piper and Orton attacked him on the first episode of Saturday Night's Main Event. Later in the evening, Orndorff ran to the ring to even the sides when Piper and Orton were preparing to double team Hulk Hogan. He solidified his babyface status by publicly firing manager Bobby Heenan shortly afterwards.
Orndorff and Hogan started teaming up to feud with Piper and Orton, facing them in tag team competition all over the country. Orndorff’s feud with Piper and Orton continued to rage on while Hogan started to defend his title against other contenders; Orndorff faced both Orton and Piper in individual competition, usually without a conclusive outcome. After Orndorff fired Bobby Heenan as his manager, Heenan placed a $25,000 bounty on Orndorff, payable to anyone who could injure him. When no one succeeded, Heenan upped the bounty to $50,000. One of the first men to try and claim the new, higher bonus was Roddy Piper himself, but their matches got so out of hand that Bruno Sammartino was appointed as a special referee in the hopes of keeping peace. Instead of keeping peace, Sammartino became a target for Orton and Piper, which led to Orndorff and Sammartino teaming up. Orndorff teamed with a variety of opponents in his fights with Piper and Orton, including André the Giant. In February 1986, Bobby Heenan used a match between Hulk Hogan and Don Muraco as an opportunity to have King Kong Bundy attack Hogan, setting up their WrestleMania 2 match. While Hogan fought off Bundy, Orndorff battled Don Muraco in a match that ended in a double count out.
Orndorff’s frustrations were further fueled by Adrian Adonis, who took every opportunity that he could to mock Orndorff (including referring to him as "Hulk Jr."), saying that he had gone soft from teaming with Hogan. Adonis kept on irritating Orndorff, going so far as daring Paul Orndorff to prove just how close his relationship with Hulk Hogan really was. During a televised phone call to Hulk Hogan, Orndorff was told that Hogan was too busy training to come to the phone, something which aggravated Orndorff to no end. The next time that Hogan and Orndorff teamed up, against the Moondogs, Orndorff wrestled most of the match by himself in an attempt to upstage Hogan, scoring the winning pin. The next week, during a tag match where Hogan and Orndorff faced the massive duo of Big John Studd and King Kong Bundy, Hogan and Orndorff accidentally collided and Hogan knocked Orndorff off the apron. When Studd and Bundy started to double team Hogan, Orndorff did not help out; he looked like he had hurt his eye in the collision. It was not until Studd and Bundy had Hogan in a compromised position that Orndorff reentered the ring to fend off Studd and Bundy. Orndorff then helped Hogan to his feet and raised his hand in the air and gave Hogan a clothesline followed by a piledriver.
Orndorff soon reunited with manager Bobby Heenan and once again feuded with Hulk Hogan, including a memorable outdoor match in Toronto which drew an estimated 76,000 fans. After a series of matches with no clean outcome it was decided that Hogan and Orndorff would clash in a steel cage match on Saturday Night's Main Event. The cage match saw both Orndorff and Hogan climb over the top of the cage and touch the floor at the same time. After reviewing the footage it was decided that it was a draw and the match was restarted. Once the match restarted, Hogan easily exited the cage to win the match following a leg drop, ending their feud. Their half-year long feud is one of the most notable (and profitable) feuds in the history of pro wrestling.
During the Hogan feud, Orndorff seriously injured his right arm in a weightlifting accident. Because he was in the middle of his big money run with Hogan, he did not want to take the time off to have the surgery to properly treat it, opting instead to continue to wrestle. After the program with Hogan ended, Orndorff worked a reduced schedule for a few months before he was forced to take some time off because of the injury. While Orndorff was away from the WWF, Bobby Heenan brought in a new man "Ravishing" Rick Rude to take Orndorff’s place in the Heenan Family. Orndorff returned to the ring specifically to fire Bobby Heenan and to feud with Rick Rude. Orndorff took Oliver Humperdink as his manager in his fight with Rude and Heenan. Orndorff’s last “big" appearance was at the inaugural Survivor Series on November 26, 1987, where he teamed with Hulk Hogan, Bam Bam Bigelow, Ken Patera, and Don Muraco to take on Andre the Giant, the One Man Gang, King Kong Bundy, Rick Rude, and Butch Reed. Early in the match, Rude eliminated Orndorff with a roll-up.
On February 3, 2005, Orndorff was announced as one of the inductees for the Class of 2005 into the WWE Hall of Fame. He was inducted on April 2 at the Universal Amphitheatre in Los Angeles, California by Bobby "The Brain" Heenan.
On April 6, 2014, Orndorff made an appearance at WrestleMania XXX. This marks the first time being on WWE television since the 2005 Hall of Fame. He appeared with Rowdy Roddy Piper, Hulk Hogan, Mr. T, Pat Patterson who was part of the main event at the first WrestleMania and Gene Okerlund who was conducting an interview with Hogan when the rest appeared.
On August 11, 2014 Orndorff made an appearance at Hulk Hogan's birthday celebration on Monday Night Raw, celebrating in the ring with many other WWE legends, including Hogan himself, Ric Flair, Kevin Nash, Scott Hall, Gene Okerlund, Jimmy Hart, and Roddy Piper.