This study was designed to clarify bilaterally effect of long-time varicocele on left and right testes and to identify the effect of varicocele on maturation divisions during spermatogenesis. Moreover, the percentage of seminiferous tubules (STs) with I-VIII and IX-XIV stages of spermatogenesis and sperm parameters such as sperm motility and abnormality types were evaluated. The left varicocele was induced in test group (n=18) and control-sham animals (n=6) were gone under simple laparatomy. The test group further sub-divided into three subgroups based on the duration of varicocele (4, 6 and 8 months after varicocele induction). The histological alterations, spermiogenesis index (SPI), Sertoli cells (SCs), cytoplasmic lipid and alkaline phosphatase (ALP), germinal cells first and second maturation divisions, spermatogenesis stages, natural mating and sperm characteristics (count, motility and abnormality) were evaluated. Histological results showed that the varicocele-induced damage affected both stages of I-VIII and IX-XIV and up to 20% of the STs exhibited negative SPI and SCs degeneration. After 8 months, majority of STs demonstrated a remarkable reduction in the first and second maturation division in both of the testes. Nevertheless, the right testicles were manifested with significantly (P < 0.05) lower detrimental features in comparison with the left ones. Following varicocele induction the sperm count, viability and motility reduced time-dependently. Our data suggested that monolateral varicocele-induction affected both right and left testicles simultaneously albeit with differences. The varicocele-induced injuries were manifested as negative SPI and SCs degeneration, which may have led to poor sperm quantity and quality.