In 1976, Hansen made his debut for the World Wide Wrestling Federation (WWWF) and only two months after he began competing for the company, he began feuding with the WWF Heavyweight Champion Bruno Sammartino over the title. During a title match, Hansen broke Sammartino's neck while they were wrestling and it was from this incident that both Hansen and promoters claimed that Sammartino's injury came about from the enormous power of his lariat. However, a botched powerslam is what actually caused Sammartino's injury. After Sammartino recovered, Hansen faced him for the WWWF Heavyweight Championship once again, but was unsuccessful. He left the promotion soon after. He returned in 1980, rekindling his feud with Sammartino and facing Pedro Morales and Andre the Giant on several occasions. He also developed a heated feud with then-WWF Champion Bob Backlund which culminated in a steel cage match at Madison Square Garden.
On April 13, 1990, the WWF held a supershow called Wrestling Summit at the Tokyo Dome in Tokyo, with the scheduled main event of Hulk Hogan squaring off against Terry Gordy. Gordy was scheduled to lose to Hogan, but Gordy refused. As a result, Hansen was a last-minute replacement for Gordy. This would be Hansen's last appearance for the WWF.
On March 21, 2016, WWE announced Hansen will be inducted into the WWE Hall of Fame.