Kangaroo Al Costello trained Sullivan in the mat wars and soon he began traveling the twenty-five regional territories throughout the U.S., Puerto Rico and Canada.

[6] From 1969 through 1973, he enjoyed a protracted stint in the WWWF as "John L. Sullivan," a mid-card babyface, losing to top-tier heels like Killer Kowalski and Toru Tanaka, but repeatedly holding the notorious Baron Mikel Scicluna to a draw, and regularly defeating low-carders like Angelo Savoldi and Johnny Rodz.

The pair appeared at the inaugural WrestleMania I event with Beefcake battling David Sammartino (seconded by his father Bruno Sammartino) to a double disqualification after Valiant slammed David on the floor before being attacked by Bruno who threw him into the ring where all four continued the fight.

After initially feuding with Tito Santana (who reclaimed the IC title from Valentine in July) and the Junkyard Dog, The Dream Team began to challenge The U.S. Express (Barry Windham and Mike Rotundo) for the WWF World Tag Team championship after Valentine had lost the IC title to Santana in July.

After this show, Valiant was phased out as manager of the New Dream Team and was then relegated to the role of a wrestler once again, as a jobber to the stars.

[9] Valiant left the WWF in March 1988, just before WrestleMania IV, and then returned to the AWA as a manager and led the Destruction Crew (Wayne Bloom and Mike Enos) to the AWA World Tag Team Championship in 1989 (defeating Greg Gagne and Paul Diamond in a tournament final).

His one-man show "An Evening with Johnny Valiant" garnered critical praise from Time Out New York, The Village Voice and WBAI Pacifica Radio.

Sullivan was struck and killed by a pickup truck at 5:30 a.m. in Ross Township, a northern suburb of Pittsburgh, on April 4, 2018.