Former junior rugby player Okoye – who has never played a competitive American football match but was an Olympic finalist in the discus last year – announced he had been offered a three-year deal by the prestigious 49ers as an undrafted free agent, almost immediately after the final draft picks were announced.
"Proud to announce I will be signing with the @49ers!" the 21-year-old said on Twitter.
Okoye had rejected offers to play professional rugby and to study law at Oxford University, with most expecting him to continue with the discus until at least the 2016 Olympics in Rio de Janeiro.
But the Londoner instead tried his hand at American football, impressing scouts at the Super Regional Combine in February and entering the draft as an unaffiliated prospect.
His physical prowess was commented on by reporters and scouts alike, and having gone to an Olympic final only two years after taking discus up seriously, the academically-gifted Okoye is regarded as a quick learner.
His fellow Londoner Tom Wort was less fortunate though. The 22-year-old linebacker, who only took up the sport two years ago after initially entering the US system as a basketball player, could still be chosen by an NFL team or a UFL or indoor football side.