The British heavyweight boxer - who trains with AJ - has described the bout as a "terrible" idea, and insisted Jake's brother, WWE superstar Logan Paul, should be concerned for his sibling.
Speaking to BBC Radio 5 Live, he added: "You don't mess around with things like this.
"I like Jake Paul and I'm not saying he shouldn't take the fight.
"I just feel like he needs to weigh up the outcomes. If I was Jake Paul's brother, I'd be very worried."
Itauma, 20, also argued that Joshua is entitled to take the payday for a fight with Paul, rather than being concerend about his legacy in the sport.
He said: "Your kids can't eat legacy. If you're talking about getting paid hundreds of millions of dollars to fight a YouTuber, why not?"
Despite Itauma's concerns, Nakisa Bidarian - Paul's manager, and co-founder of Most Valuable Promotions - dismissed the idea of the fight being "reckless".
He told BBC Sport: "I don't think it's reckless in any way shape or form.
"Jake's in a much better position than a lot of fights which happen in boxing on a regular basis. I think he has a great shot.
"AJ is big, strong, but slower. He's more vulnerable to Jake's movement. In my mind this is more sanctionable than many fights in the sport of boxing."
Paul has long expressed his interest in fighting Joshua, and had approached AJ’s promoter Eddie Hearn to set up the fight for after his cancelled bout with Gervonta ‘Tank’ Davis.
The fight was canned once a lawsuit was filed against Davis by his ex-girlfriend accusing him of battery, aggravated battery, false imprisonment, kidnapping and intentional infliction of emotional distress.
