Problem: Strong evidence suggests that the immune system plays a critical role in the progression and development of endometriosis. This study aims at assessing the endometrial immune profile in patients with endometriosis-associated recurrent implantation failures (RIFs) following in-vitro Fertilization (IVF) or Intracytoplasmic Sperm Injection (ICSI), in comparison to women with male infertility-associated RIFs. Method of Study: This case-control study compared the endometrial immune profile in women with endometriosis-associated RIFs (case group) versus those with male infertility-associated RIFs (control group). The profile was evaluated using the ratio of IL-18/TWEAK mRNA expression levels (a biomarker for angiogenesis and Th1/Th2 balance), the ratio of IL- 15/Fn14 mRNA expression levels (a biomarker for uNK cell activation/maturation), uNK cell counts, and CD56 mRNA expression levels (a marker for uNK cell mobilization). Results: The distribution of immune profiles significantly differed between the case group and the control group. The case group had fewer patients with a regulated profile (18.9% vs. 24.3%, P value 0.01) and more patients with under-activated profiles (34.2% vs. 28.4%, P value < 0.0001). Additionally, the case group had a higher proportion of immature uNK cells (46.2% vs. 39.2%, P value 0.007). The immaturity of uNK cells in endometriosis-associated RIFs appeared to be mediated by decreased IL-15 expression levels. Conclusions: The study highlights unique immune characteristics in the endometrial environment of women with endometriosis-associated RIFs, emphasizing the role of immune dysregulation in the development and progression of endometriosis.