Objective: The aim of this study was to evaluate the efficiency of the intracytoplasmic morphologically selected sperm injection (IMSI) technique compared with conventional ICSI and previous ICSI attempts in oligo-astheno-teratozoospermia (OAT) patients. Methods: The sperms were selected under high magnification ($6,600{ imes}$) and used to induce fertilization in previous ICSI patients by IMSI. These results were compared with previous conventional ICSI cycles in patients with OAT infertility. Results: These results demonstrated no significant difference in the fertilization rate between IMSI and previous ICSI cycles (67.7% vs. 65.0%). However, the pregnancy and implantation rates with IMSI were significantly higher than those of the ICSI cycles (33.3% vs. 12.5% and 14.6% vs. 5.4%, respectively; p<0.05). The miscarriage rate among pregnant patients (18.2% vs. 37.5%) showed no statistically significant difference between groups. Conclusion: Compared to conventional ICSI, this study found that IMSI increased the IVF-ET success rates in patients with OAT.