To improve the effectiveness of the sterile insect technique against the Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), our objectives in this study were two-fold. First, to evaluate the ability of sterile males of the Vienna-8 strain to survive starvation, we compared them to wild males under laboratory conditions. The second objective was to determine the effect of protein-rich nutrition on sterile male fly survival, under starvation conditions in the laboratory, under semi-natural conditions in a field enclosure, and under natural conditions in the open field. Therefore, we released marked sterile flies of the two diet regimes, protein-fed or protein-deprived, and monitored their survival by recapturing them after 4, 6, and 7 days. In the laboratory, wild males endured starvation significantly better than sterile ones and protein addition to sterile fly diet resulted in even greater reduced capability to endure starvation. On the other hand, the addition of protein to sterile-male diet did not affect their ability to survive in a field enclosure or in the open field. We conclude that under natural conditions, where food is available, sterile male fly survival is unaffected by protein-rich pre-release diet.