Early career Jennings made his professional debut on February 26, 2010. He beat Zeferino Albino by
unanimous decision over four rounds. He went on the knock out Jon Bolden in three rounds and then rematched Albino on April 30, this time he knocked Albino in the first round. He went on to beat Bernell Stewart and Randy Smith in 2010. Jennings first fight of 2011 was on the February 26. He beat Theron Johnson by unanimous decision. He next fought David Williams, who he knocked out in two rounds. On 4 June he beat Mike Miller by unanimous decision. On July 23 he rematched Theron Johnson, again beating him by unanimous decision. Jennings fought twice more in 2011, beating Alexis Mejias and Kevin Franklin. Jennings's first fight of 2012 was a ten-round bout against Maurice Byarm on January 21 at the
Asylum Arena in
South Philadelphia on the
NBC Sports Network Fight Night opening card. Jennings won the bout by unanimous decision to claim the Pennsylvania State heavyweight title. On March 24, 2012, he faced former
WBO heavyweight champion Siarhei Liakhovich. The fight took place at
Aviator Sports Complex,
Brooklyn,
New York and was televised on
NBC Sports. Jennings controlled the fight with his jab and power punches. He won the fight after Liakhovich retired at the end of round nine. Jennings then faced Steve Collins (25–1) on June 16, 2012, at the
Prudential Center,
Newark, New Jersey. The fight was co-main event as part of
NBC Sports Fight Night event, including
Tomasz Adamek vs.
Eddie Chambers. He won by unanimous decision after ten rounds to claim the
USBA heavyweight title. Jennings went on to fight two more times in 2012, knocking out Chris Koval in 35 seconds. Then stopping
Bowie Tupou in five rounds to retain his
USBA heavyweight title. Jennings fought once in 2013, on June 14, stopping Andrey Fedosov in six rounds after Fedosov did not come out for the seventh. On January 25, 2014, Jennings fought Polish heavyweight,
Artur Szpilka, at the
Madison Square Garden. Jennings knocked out Szpilka in the tenth round. Jennings's next fight was against highly ranked contender
Mike Perez, on July 26, 2014. He beat Perez by a close fought
split decision to earn a title shot as No.1 ranked contender and
mandatory challenger, for the WBC title. Jennings later signed with promoters Gary Shaw and Antonio Leonard after buying out his existing agreement with Russell Peltz.
World title challenge Jennings vs. Klitschko Jennings faced heavyweight champion
Wladimir Klitschko on April 25, 2015, in
Madison Square Garden for the
WBA (Super),
IBF,
WBO,
IBO,
The Ring, and lineal
heavyweight titles. Klitschko won the fight due to his effective use of his jab and hard right cross keeping Jennings at bay, Klitschko won via unanimous decision with two judges scoring it 116–111 and the final judge scoring it 118–109.
Jennings vs. Ortiz On December 19, 2015, Jennings faced undefeated Cuban heavyweight contender
Luis Ortiz, for the WBA
interim heavyweight title. Jennings lost the fight by
technical knockout in the seventh round after he was dropped by a left uppercut from Ortiz, who then continued to land heavy shots before the referee stepped in to stop the fight.
Comeback After not fighting for over a year following the Ortiz loss, Jennings signed with
Top Rank. Jennings returned to the ring on August 19, 2017, against journeyman Daniel Martz on the undercard of
Terence Crawford vs. Julius Indongo. He knocked out Martz in the second round. He next fought on December 9, 2017, at the
Madison Square Garden, on the undercard of
Vasiliy Lomachenko vs. Guillermo Rigondeaux. Where he knocked out Don Haynesworth in three rounds. His first fight of 2018 was against Akhror Muralimov on February 16. He knocked out Muralimov in the third round. Jennings's next fight took place on April 28, 2018, where he beat Joey Dawejko by unanimous decision over ten rounds.
Jennings vs. Dimitrenko 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. He won by technical knockout in the ninth round. This was a highly criticized stoppage with Dimitrenko even saying he was "still able to fight" and that "we are not children"
Jennings vs. Rivas In his next fight, Jennings faced Oscar Rivas, ranked #10 at heavyweight by the IBF. Jennings outboxed Rivas thourghout most of the fight, however, Rivas, knowing only a knockout could bring him the win, came out swinging in the last round and managed to TKO Jennings after dropping him twice in a row.
Jennings vs. Joyce In his following fight, Jennings faced Joe Joyce, who was ranked #14 by the WBC at the time. Jennings was the better man in the first round, but after that Joyce took control and dominated through most of the fight. Joyce won the fight on all three judges' scorecards, 118–109, 117–110 and 115–112. ==Personal life==