The ultrastucture of the snake Eryx jayakari (E. jayakari) mature sperm has not been published. Therefore, the present study was conducted to elucidate the sperm ultrastructure of this species in comparison with that of other reptilian species. The present investigation has shown that mature spermatozoa of Eryx jayakari are filiform in shape averaging 45 μm (mean of 10) in length with a curved head measuring 9 μm. The acrosomal complex, which involves the acrosomal cap and subacrosomal material, measures 2.5 μm. The nucleus is 6.5 μm in length, the neck approximates 1 μm and the tail (midpiece, principal piece and endpiece) is maximally 35 μm in length. The different tail pieces vary in diameter, being the largest at the midpiece (0.66 μm), diminished at the principal piece (0.36 μm) and the least at the endpiece (0.25 μm). The midpiece, the longest tail piece, is composed of mitochondrial and fibrous sheaths encircling the microtubular axoneme. The mitochondria are rod-shaped having linear cristae but no dense bodies interrupt their arrangement. The principal tail piece consists of the microtubular axoneme surrounded by the fibrous sheath. The endpiece involves only an axoneme enveloped within the plasmalemma of the spermatozoon. The present findings were discussed in relation to other relevant studies. It was concluded that the general ultrastucture of the E. jayakari spermatozoon conforms to that reported to be typical of squamates.