Purpose: To investigate if including evaluation of acrosome index (AI) in the semen analysis of teratozoospermic samples could help to predict for which patients intracytoplasmic sperm injection (ICSI) is necessary. Methods: The fertilization rate, pregnancy rate, and percentage of good quality embryos were compared after performing conventional in vitro fertilization (IVF) and ICSI, respectively, using sibling oocytes. The role of AI was evaluated by dividing patients into two groups; Group A (AI < 7%) and Group B (AI ≥ 7%). Results: A significant difference in fertilization rate was observed between Group A and B after conventional IVF. In Group A, the fertilization rate, embryo transfer rate, and percentage of good quality embryos were higher after ICSI than after IVF. In Group B, the fertilization and pregnancy rates were numerically but not significantly higher after IVF compared to ICSI. Conclusion: Evaluation of acrosome index will not accurately predict fertilization, although this study shows that a sperm sample with less than 5% normal forms and an AI greater than 7% may achieve a mean fertilization rate >70% after conventional IVF.