In 2016, Smith became the first boxer to score a stoppage victory over former undisputed middleweight world champion Bernard Hopkins.
Smith made his professional debut in October 2009 defeating David Brown by technical knockout in the first round in Connecticut.
[4][5][6] In April 2016, Smith defeated Brazilian boxer Fabiano Pena (16-4-1 12 KOs) via a 2nd-round TKO winning 15 straight fights and continuing to rise up the ranks.
[7] It was announced that Smith would be fighting the #2 WBC contender, former world title challenger Andrzej Fonfara (28-3, 16 KOs) for the WBC international light heavyweight title at the UIC Pavilion in Chicago, Illinois on June 18, 2016, in a scheduled 10 round fight in the main event of the Premier Boxing Champions card on NBC.
[8] In an 'Upset of the Year' in the light heavyweight division, Smith won the title by defeating Fonfara via a 1st-round technical knockout.
[12] Former multiple weight world champion Bernard Hopkins (55-7-2, 32 KOs) announced he would be having a farewell fight at The Forum in Inglewood, California on December 17, 2016.
Hopkins would be coming out of a two-year layoff having last fought in 2014 in a decision loss to then unified light heavyweight champion Sergey Kovalev.
Smith retained his WBC International light heavyweight title with the win and spoke of his respect for Hopkins in the post-fight, stating he is 'a true champion'.
[21] On May 12, Boxing Scene confirmed a deal was in place for Smith to fight Cuban light heavyweight contender Sullivan Barrera (19-1, 14 KOs).
Early reports indicated the fight would be part of a HBO triple-header also featuring Miguel Berchelt defending his WBC super featherweight title against mandated Takashi Miura on July 15, 2017, in Inglewood, California.
At first the HBO commentary thought the referee had made a mistake, but were later told, both fighters agreed to the fight being 10 rounds.
[31] On May 9, it was announced that Smith would make his return to the ring at the Mohegan Sun Arena in Montville, Connecticut on June 30, 2018.
[35] In September 2018, it was reported a deal was being worked out for Smith to challenge Russian boxer Dmitry Bivol for his WBA light heavyweight title.
On October 15, Yvon Michel told the LA Presse that Smith was in talks to challenge his fighter, the IBF champion Artur Beterbiev (13-0, 13 KOs), on a card that would take place on DAZN.
[37] According to Le Journal de Montréal on November 3, Beterbiev decided against defending his title on December 15 against Smith and instead stated he would fight him in early 2019 instead.
[38] On March 9, 2019, Smith Jr challenged WBA champion Dmitry Bivol for his light heavyweight version of the belt.
[41] In what was a WBO title shot eliminator, Smith Jr, usually regarded as more of a brawler, showcased his boxing skills en route to a ninth-round KO win.
[42] On April 10, 2020, Smith Jr. challenged Maxim Vlasov for the vacant WBO World Light Heavyweight Title.
Smith was knocked down three times in the first two rounds as he was defeated via second-round technical knockout, losing his WBO title.