Biggie, whose birth name was Christopher Wallace, was gunned down on March 9, 1997, in Los Angeles. He was only 24.
His murder came only six months after the death of another iconic rapper, Tupac Shakur. Both killings remain unsolved.
"I think I'll always feel some sort of responsibility because I'm in this thing with him. He's my artist," Diddy said today on "The Wendy Williams Show."
The music mogul and record company executive then recalled a conversation the two had right before he was killed.
"He was supposed to go to London that night and I let him talk me into not going to London and staying in L.A.," Diddy detailed. "That's something that really bothered me throughout my life. Sometimes you have to really go with that decision in your gut and in my gut it was like, 'You need to get on the plane.'"
Diddy said looking back he has regrets.
"This is God's world. It's his plan but honestly that's one of the things I regret is not making sure that he went to London," he said.