Tommy Fury - more known for his time on Love Island rather than his time in the boxing ring - was expected to take on Jake Paul in December last year, only for him to pull out due to a broken rub and a chest infection.
Both fighters are undefeated with Fury at 8-0 while Paul - who rose to fame through social media - is 5-0.
Paul defeated Fury's replacement Tyron Woodley in his most recent fight and delivered a sensational knockout. His other wins are over ex-NBA star Nate Robinson and former MMA champion Ben Askren.
Fury - who outpointed Daniel Bocianski earlier this year in a six-round fight - announced that he had signed the contract to fight his rival on Thursday.
"Just to let you all know, the fight on August 6 is going ahead, the contract has been signed," said Fury.
"After weeks and weeks of waiting for Jake Paul to sign up to the drugs testing - and potentially putting the fight at risk - he's finally signed up to the drug testing.
"We've agreed a contract that we're happy with, so the fight is going ahead and I'll see you August 6."
It comes following taunts from Paul on Wednesday as the American revealed the details of the contract, claiming it included a $2m purse, VADA testing and 'tampons'.
Paul also confirmed the contest on his Twitter page.
He said: "It's official, I'm taking this little Fury's head off. Amanda Serrano and I dual main-event at the Mecca of boxing."
The showdown will take place at Madison Square Garden with a press conference set to happen next Wednesday in New York.
Showtime Boxing will broadcast the fight in America while BT Sport is expected to win the rights in the UK although it is yet to be confirmed.
The fight will be promoted by Paul's Most Valuable Promotions, with a launch event scheduled for next Wednesday in New York. Tickets will go on sale on the same day. It will be shown on Showtime Boxing in America, with no UK broadcaster yet announced.