He won the WWWF Championship on May 17, 1963, defeating "Nature Boy" Buddy Rogers in just 48 seconds. Distraught and surprised, Rogers quickly left the ring.
Rogers and Sammartino did face each other two months later at Madison Square Garden in a tag team match, with Rogers & Handsome Johnny Barend defeating Bruno & Bobo Brazil 2 falls to 1. Sammartino did not trust Rogers (who had a reputation for taking cheap shots) and the two did not work together very much during the match. Rogers pinned Sammartino for the third and deciding fall.
Rogers retired prior to their scheduled title rematch on October 4, 1963, in Jersey City, NJ's Roosevelt Stadium. Sammartino instead that night had his first match against new #1 contender, Gorilla Monsoon (Monsoon won on disqualification, starting a monumentally successful feud).
Sammartino headlined cards that filled both the third and current Madison Square Gardens on a monthly basis. He battled the top bad guys of his time, including Killer Kowalski, Giant Baba, Gene Kiniski, Dr. Bill Miller, Dr. Jerry Graham, Bull Ramos, Hans Mortier, Waldo Von Erich, "Crusher" Reginald Lisowski, Johnny Valentine, The Sheik, Freddie Blassie, Curtis Iaukea, Tarzan Tyler, Bill Watts, Gorilla Monsoon, Professor Toru Tanaka, Handsome Johnny Barend, The Kentucky Butcher and George "The Animal" Steele.
On January 18, 1971, Sammartino lost the championship at Madison Square Garden to Ivan Koloff. The crowd was so stunned into silence that Sammartino thought his hearing had been damaged. After the pin, Koloff slowly walked across the ring while the ref raised his hand three times. The announcer came into the ring with the belt but, fearful of a riot, did not present it to Koloff. Koloff left the ring while Sammartino stayed inside to keep the crowd's attention off Koloff. As Sammartino left the ring, people started crying.
Three weeks later, Pedro Morales beat Koloff to win the title; Sammartino congratulated Morales as the new champion was announced.
Soon after, Bruno and champion Morales teamed up for a series of tag matches. In a televised match, Professor Tanaka blinded both men with salt and they were maneuvered into fighting each other. When their eyes cleared, to the surprise of the crowd, they kept fighting each other.
On September 1, 1972, Sammartino and Morales wrestled to a 75-minute draw at Shea Stadium in New York. During the match, George Steele tried to interfere, but Steele was restrained by an army of police, before Steele could enter the ring.
Eventually, on December 10, 1973, Sammartino regained the WWWF Championship by defeating Stan Stasiak who had won the title from Pedro Morales nine days earlier in Philadelphia.
In his second reign, Bruno defeated contenders such as John Tolos, Bruiser Brody, Spiros Arion, Ken Patera, Bugsy McGraw, Freddie Blassie, Baron Von Raschke, Waldo Von Erich, Ivan Koloff, "Superstar" Billy Graham, Don Leo Jonathan, Angelo Mosca, Ernie Ladd, Big Bob Duncum and Nikolai Volkoff. He also encountered old foes Killer Kowalski & George Steele. His second title run lasted three years, four months, and twenty days.
In early 1977, after suffering the broken neck and many other ailments, Bruno informed McMahon Sr. that he was done with his second title reign. It ended in Baltimore on April 30, 1977, when he was defeated by "Superstar" Billy Graham. In a controversial ending, Graham had both feet braced on the ropes (which is illegal in pro wrestling) while successfully pinning Sammartino.
Despite a very long and financially successful series of re-matches against Billy Graham, Sammartino was unwilling to regain the title. His final attempt was in Philadelphia, just a few days before Graham was scheduled to lose the title to Bob Backlund. The Philly match was the only documented instance of Sammartino losing a Steel Cage Match. He lost by accidentally knocking a bloody and battered Graham through the cage door.
One of the most emotional feuds of Sammartino's career started on January 22, 1980, when his former student Larry Zbyszko violently turned against him during a scientific wrestling exhibition, broadcast on the World Wrestling Federation's Championship Wrestling show. Sammartino, shocked and hurt by Zbyszko's betrayal, vowed to make Zbyszko (whom Bruno described as a "Judas") pay dearly. Their feud culminated on August 9, 1980, in front of 36,295 fans at Shea Stadium. As the main event of 1980's Showdown at Shea, Sammartino defeated Zbyszko inside a steel cage.
At the inaugural WrestleMania at a sold out Madison Square Garden in 1985, Sammartino was in his son's (David) corner, for his match against Brutus Beefcake. The match ended in a double-disqualification after the Sammartinos began brawling with Beefcake and his manager Johnny Valiant. He returned to in ring action soon after with his son, as they wrestled against Beefcake & Valiant at Madison Square Garden. The Sammartinos also teamed against Paul Orndorff and Bobby Heenan in various arenas. Despite being in his early-50's, Sammartino frequently proved to be in much better physical shape than his opponents, often leaving them "blown up" by the middle of the match.
Sammartino's most notable feud during this run was with "Macho Man" Randy Savage. An irate Sammartino attacked Savage during a TV interview, after Savage bragged about injuring Ricky Steamboat, by driving the timekeeper's bell into Steamboat's throat during a televised match.
Sammartino defeated Savage in a lumberjack match for the WWF Intercontinental Championship via disqualification at the Boston Garden. This allowed Savage to keep the belt, as titles cannot change hands via count out or disqualification.
Sammartino would often be teamed with Tito Santana and his old enemy George "The Animal" Steele (who was a face at this point in his career) to wrestle Savage and "Adorable" Adrian Adonis. The climax of the their feud came was a victory for Sammartino & Santana in a steel cage match in Madison Square Garden.
Sammartino also engaged in a feud with Rowdy Roddy Piper after Piper insulted his heritage on a segment of Piper's Pit at Madison Square Garden. Sammartino faced Piper in both singles & tag matches. Sammartino teamed with Paul Orndorff in his matches against Piper, while Piper would tag with his "bodyguard", Ace "Cowboy" Bob Orton. Sammartino would eventually get the upper hand in the feud, by defeating Piper in a steel cage match at the Boston Garden.
In 1986 Sammartino competed in a 20 man battle royal at WrestleMania 2 in at the Rosemont Horizon in Chicago. The battle royal featured not only professional wrestlers but also professional football players. Sammartino was eliminated by Killer Kowalski protege Big John Studd. André the Giant would go on to win the battle royal.
Later on in 1986 Sammartino would team with Jake "The Snake" Roberts, and Santana in a 6 man Elimination Tag Team Match against The Hart Foundation & The Honky Tonk Man. Sammartino was the sole survivor of the match pinning the Honky Tonk Man for the win.
Sammartino's last major feud came in the summer of 1987 against The Honky Tonk Man for the WWF Intercontinental Championship. Although he dominated the matches against the champion, Sammartino never won the title, winning most of his matches by count out or disqualification.
Sammartino also feuded with Hercules Hernandez during this time. Sammartino had his last singles match in the WWF against on August 28, 1987 as he defeated Hercules via count out.
Sammartino's final WWF match saw him team with Hulk Hogan to defeat King Kong Bundy and One Man Gang. Sammartino continued doing commentary on the WWF Superstars of Wrestling until March 1988.
In 2013, Sammartino accepted an invitation for induction into the WWE Hall of Fame, after having declined several times in prior years. The ceremony took place at Madison Square Garden on April 6, 2013. Afterwards Sammartino shook hands with Vince McMahon. Sammartino appeared on Raw on October 7, which was in Pittsburgh, and received a birthday greeting in his hometown.