Objective: Spermatozoa are specialized cells that remain inactive and must undergo posttranslational modifications such as phosphorylation for cellular processes including capacitation. During capacitation spermatozoa gain hyperactive motility interact with zona pellucida (ZP) and undergo acrosome reaction. In this study we have investigated the protein tyrosine phosphorylation pattern of spermatozoa in normozoospermic and infertile teratozoospermic men referred to Avicenna Infertility Clinic in Tehran Materials and Methods: Semen samples were collected and spermatozoa were isolated using percoll gradient centrifugation. Spermatozoa were then incubated for 6 h at 37ºC in 3% Bovine Serum Albumin- supplemented Haḿs-F10 for capacitation. Total proteins of spermatozoa were extracted following standard protocol. To characterize phosphorylated proteins two dimensional gel electrophoresis (2DE) coupled with western blotting was performed. Results: Our results from 2DE and western blotting showed that during capacitation some proteins become phosphorilated in spermatozoa from normozoospermic men but not in teratozoospermic men Conclusion: These findings suggest that compromised sperm protein phosphorylation in teratozoospermermic men can potationally be responsible for diminished capacitation and low fertilization success in this group.