Background: infertility is an increasing medical and social problem. Delayed childbearing exposes couples to increased risk of causes of infertility including endometriosis, pelvic infection, and poor egg and sperm quality. Many infertile couples turn to in-vitro fertilization (IVF). Objective: to analyze and compare between the peripheral blood NK cells (CD56+ CD69+ ) in women with repeated ICSI failure. Patients and Methods: the current study is a case control study. One hundred women were included and divided into two groups: The study group included 50 women with history of unexplained infertility and repeated implantation failure in their ICSI attempts and a control group which included 50 normal, non-pregnant and fertile women. Results: the current study revealed that there was a highly statistically significant difference between control and case groups regarding CD3- CD56+dim NK percentage with a p-value <0.0001. The current study revealed that there was a statistically significant difference between control and case groups regarding CD3- CD56+dim CD69+ NK cells percentages with a p-value 0.001. Conclusion: there was a highly statistically significant difference between control and case groups regarding CD3- CD56+dim NK percentage. Also the study showed that total CD56+dim NK had a very good predictive value as it had a sensitivity of 80.0%, a specificity of 66.7%, a PPV of 73.3% and a NPV of 78.8%.