Background and Aim: Male infertility is increasing worldwide. There is now emerging evidence that nutritional status is regarded as a critical determinant of normal reproductive function. Hence, today, the role of dietary nutrition has attracted the attention of researchers. Thus, the present study was conducted to elucidate the effects of tail fat (TF) enriched diet on male rat reproductive function.Materials and Methods: In this experimental study, 30 adult male Wistar rats were randomly allocated into three equal groups and were fed with either standard diet (control) or standard diet enriched with 10 % of TF oil or standard diet enriched with 20% TF for 5 consecutive months. Finally, the rats were euthanized, the weights of their bodies, and their testes were measured. Then, the testes were dissected and the sections were stained with Hematoxylin-Eosin for quantitative histopathological examination. Besides, blood samples were collected for testosterone (T) assessment.Results: Compared to the control group, the rats fed with a diet enriched with 20% TF had significantly (P≤0.05)more body weight, while, their testes weight significantly (P≤0.0001) decreased. Also, histological changes showed that TF, in a dose dependence manner, significantly decreased germinal layer, seminiferous area, and spermatogonia number in the rats’ testes. There was no significant difference in T concentration between the groups.Conclusion: It was clearly found that excessive and long term intake of TF can be causative of hypogonadism and increase infertility in male rats.