[4][5] He beat Igor Pawel Jakubowski from Poland on points and made it to the Round of 16, where he lost to eventual bronze medalist Erislandy Savón of Cuba.
[citation needed] On 18 January 2017, Okolie announced his decision to turn professional, signing with Eddie Hearn and Matchroom Sport to compete in the cruiserweight division.
[6][7] His next bout took place in Glasgow, Scotland at The SSE Hydro on 15 April as part of the undercard for the world Ricky Burns vs. Julius Indongo super lightweight unification fight.
[12][13] Okolie fought on the Kell Brook vs. Errol Spence Jr. IBF world title undercard at Bramall Lane in Sheffield on 27 May, defeating Rudolf Helesic in the first round.
[14] On 1 July, Okolie recorded his fourth straight first-round stoppage win against Russell Henshaw.
Other prospects on the card included Conor Benn and fellow Olympians Joshua Buatsi and Joe Cordina.
Following the win, Okolie spoke to Sky Sports about going the distance, "It was useful to go the rounds, but was tough against an awkward opponent.
"[17] Okolie next fought on 28 October on the Anthony Joshua vs. Carlos Takam undercard at the Principality Stadium in Cardiff, Wales.
[21] In front of 8,000 fans in attendance, Okolie scored a quick knockdown in the opening round, en route to a dominant one-sided unanimous decision (UD) win to capture the vacant WBA Continental title.
In round six, Okolie landed a right hand to Chamberlain, forcing his glove to touch the canvas for a second knockdown.
[24] On 16 April 2018, Commonwealth cruiserweight champion Luke Watkins (13–0, 9 KOs) called out Okolie for a fight in the future.
[25] Nine days later, the Swindon Advertiser reported that Okolie's promoter, Eddie Hearn, had given the bout the green light to go ahead.
[30] On 7 August, Eddie Hearn announced the fight was confirmed and would take place on the Anthony Joshua vs. Alexander Povetkin undercard on 22 September at the Wembley Stadium in London on Sky Sports Box Office.
[33][34][35] On 26 October 2019 Okolie fought Yves Ngabu, ranked #9 by the IBF, #12 by the WBO and #13 by the WBA at cruiserweight.
[37] They had been scheduled to face each other on the undercard of Anthony Joshua vs. Kubrat Pulev on 12 December 2020, but the fight was postponed when Głowacki tested positive for COVID-19.
Okolie also revealed that his promoter Eddie Hearn had made a deal with him, promising to buy him a watch if he succeeded in becoming a world champion: "Four or five years ago, Eddie Hearn saw a boy from Hackney and said 'if you win a world title, I'll buy you a gold Rolex Sky Dweller'.
[46] In a scrappy bout that featured a lot of grappling and rabbit punches, Okolie retained his world title with a unanimous decision victory, with judges' scorecards of 117–110, 116–111 and 115–112 in his favour.
[47] Okolie fought long-time friend Chris Billam-Smith at the Vitality Stadium in Bournemouth on 27 May 2023.
[54][55] He made his first appearance at heavyweight on 7 December 2024, with an opening round knockout of German boxer Hussein Muhamed at Wembley Arena in London.