The bout has been pushed back to UFC 117, UFC President Dana White confirmed to MMA Fighting.
"Making sure Alves is 1000 percent healthy," White replied via text when asked the reason for the postponement.
The 26-year-old Alves had brain surgery on March 31 to separate an artery from a vein in his brain, an irregularity that was discovered just days before he was supposed to meet Fitch at UFC 111 in Newark, N.J.
Fitch defeated late replacement Ben Saunders at the event, and the UFC re-booked Fitch-Alves for UFC 115 in June, but now it appears the company will err on the side of caution and give Alves a little more time to heal and prepare.
UFC 117 has not yet officially been announced by the UFC, but is expected to take place on August 7 in Oakland, Calif.
Alves and Fitch squared off once before in June 2006, with Fitch earning a second-round TKO victory. Since then, the two have rocketed up the welterweight top 10 list and are considered by most to be top contenders behind champion Georges St. Pierre.
Alves has not fought since last July's UFC 100, when he lost to St. Pierre via unanimous decision.