Matchroom Boxing have added five fights to the Anthony Joshua vs Oleksandr Usyk card on September 25.
His bout against the former undisputed world cruiserweight champion sold out within 24 hours, meaning 60,000 fans will be there on fight night.
Eddie Hearn of Matchroom Boxing has now announced the bulk of the undercard.
Okolie is the chief support as he defends his WBO world cruiserweight title against his mandatory challenger, Dilan Prasovic.
The undefeated Brit defeated Krzysztof Glowacki to win the vacant belt. He rounded off a superb performance by stopping his durable opponent in the sixth round.
Prasovic is unbeaten from his 15 fights (12 wins via TKO/KO). He last fought in May as he beat his compatriot Tomislav Rudan via knockout.
Elsewhere, Callum Smith will return to the ring for the first time since his unanimous decision defeat to Saul 'Canelo' Alvarez last December.
Smith is now fighting at light heavyweight and his first bout in the division is against Lenin Castillo.
The 33-year-old has a record of 21-3-1. He lost via unanimous decision against WBA world light heavyweight champion Dmitry Bivol in October 2019.
Also on the card, Maxim Prodan will defend his IBF international welterweight title against Florian Marku.
This fight was originally set for Fight Camp Week Two on August 7, but Marku had to pull out due to injury.
Further down the card, Campbell Hatton has his fourth pro fight against Izan Dura, while Christopher Ousley and Khasan Baysangurov do battle over the vacant WBA inter-continental middleweight title.
"It's two Olympic gold medalists; It's the unified heavyweight world champion against the [former] undisputed cruiserweight champion of the world [Usyk], who is on the pound-for-pound list.
"It's a proper fight. So am I nervous? Yeah.
"I'm excited because I know how good AJ is, and I know these are the kind of fights that he can prove he's the best heavyweight in the world.
"He is the best heavyweight in the world, and that's why I believe he'll win the fight. I think it'll be tough, I think it'll be tricky, but I believe he wins.
"But what a great fight. If you can't get up for nights like this, you should pack it in, mate.
"A heavyweight world championship at Tottenham Hotspurs. The ground is unbelievable. It's going to be a night to remember."