He was the father of wrestlers Barry and Kendall Windham, father-in-law of Mike Rotunda, and the maternal grandfather of Bo Dallas and Bray Wyatt.

After football, at the urging of Wahoo McDaniel, Windham trained with Joe Blanchard in Corpus Christi, Texas and later with Verne Gagne and became a professional wrestler in the American Wrestling Association.

Before he left to recover from his wound, Mulligan participated in a Madison Square Garden match against Bruno Sammartino, who was making his first appearance at the arena since the end of his nearly eight-year championship reign.

In wrestling terms, everybody "got over" – the building was sold out to the delight of promoter Vincent J. McMahon, Sammartino made a strong return to New York and Mulligan, who was in no condition to work an actual match, received a large pay-off to aid his recovery.

Mulligan returned for his last match on May 23, 1993, at WCW's Slamboree '93: A Legends' Reunion in a six-man tag teaming with Wahoo McDaniel and Jim Brunzell against Don Muraco, Dick Murdoch and Jimmy Snuka in a no contest.

Mulligan and his Blackjacks partner, Jack Lanza were inducted into the WWE Hall of Fame[5] on April 1, 2006, by their manager, Bobby Heenan.

In 1990, Blackjack Mulligan and his son Kendall Windham were arrested by the US Secret Service in a joint investigation with the Florida Department of Law Enforcement (FDLE) for counterfeiting.

[6] In 2007, Windham published his book titled True Lies and Alibis, which tells about his personal life and his professional wrestling career.

In 2012, Windham, a born again Christian, was ordained a minister by Divine Hearts Ministry located in Lake Saint Louis, Missouri.

In July 2015, Windham was named as a defendant in a 2015 lawsuit filed by WWE after they received a letter from him indicating that he intended to sue them for concussion-based injuries sustained during his tenure with them.

British wrestler Laurence (Laurie) Coulson (Coulton) was billed as "Black Jack Mulligan" (and related variants) while wrestling for Joint Promotions in the 1970s and 1980s.