Introduction: Morphology and ultra-structure of myoid and sertoli cells were studied in patients with non-obstructive azoospermia who were admitted to testicular sperm extraction (TESE) and intracytoplasmic sperm injection (ICSI), by transmission electron microscopy (TEM). Materials and Methods: 12 biopsies of testicular tissues from patients with non-obstructive azoospermia referred to Royan institute were used as a patient group, another 5 biopsies from person with prostate cancer were used as a control group. The tissues were fixed and processed for TEM, and Sertoli and myoid cells were examined under TEM. Results: Myoid cells of the patient group had lost their slender shape and orientation in relation to the wall of seminiferous tubules. These cells were separated by increased amount of collagen fibers, furthermore, their polarity was different from normal and the nuclear shape changed. Sertoli cells were round to ovoid in shape, and the nuclei were more regular in shape than that of the normal with peripherally located nucleoli. Conclusion: Sertoli cells in the patient group were immature or undifferentiated. This may have resulted in other changes in the testicular tissues such as the alteration in myoid cells and basement membrane, moreover, the immaturity of Sertoli cells may be the cause for the failure in initiating or triggering normal process of spermatogenesis.