Jennings had an amateur record of 13–4 including a win over future UFC heavyweight champion Stipe Miocic.

He reached the finals of the 2009 National Golden Gloves tournament, losing by decision to veteran Lenroy Thompson.

Jennings won the bout by unanimous decision to claim the Pennsylvania State heavyweight title.

[4] Jennings then faced Steve Collins (25-1) on June 16, 2012, at the Prudential Center, Newark, New Jersey.

On January 25, 2014, Jennings fought Polish heavyweight, Artur Szpilka, at the Madison Square Garden.

Jennings later signed with promoters Gary Shaw and Antonio Leonard after buying out his existing agreement with Russell Peltz.

[10] Jennings returned to the ring on August 19, 2017, against journeyman Daniel Martz on the undercard of Terence Crawford vs. Julius Indongo.

He next fought on December 9, 2017, at the Madison Square Garden, on the undercard of Vasiliy Lomachenko vs. Guillermo Rigondeaux.

Jennings's next fight took place on April 28, 2018, where he beat Joey Dawejko by unanimous decision over ten rounds.

On June 27, 2018, it was announced that Jennings would take on German heavyweight contender Alexander Dimitrenko in a twelve-round main event on August 18, 2018, at the Ocean Resort Casino, Atlantic City, New Jersey.