Safin, who plans to retire this month, said in an interview with L'Equipe newspaper on Tuesday that Agassi should "give his titles, his money and his Grand Slam titles" back.
"I'm not defending the ATP, but what he said put it in a delicate position," Safin said. "The ATP allowed him to win a lot of tournaments, a lot of money. It kept his secret. Why does he need to be so cruel with it?"
Agassi, who retired in 2006, won 60 titles, including eight Grand Slams, during his career. He recently told The Associated Press that he had to speak about his lies because he couldn't live with it anymore.
"If he is as fair play as he says he is, he has to go to the end," Safin said. "You know, the ATP has a bank account and he can give the money back if he wants."
Safin, who will retire after this week's Paris Masters, won the 2000 U.S. Open and 2005 Australian Open. The 29-year-old Russian said he isn't going to write his autobiography when his career will be over.
"Me, I don't need money," he said. "The question is: Why did he do this? What is done is done. Does he hope to sell more books? It's absolutely stupid."