Background: Fertility in male animals is an important issue in veterinary medicine. Exposure to severe crowding and fattening may affect the fertility of these animals. Objectives: This study compares the effect of oxidative stress caused by overcrowding or obesity on testicular tissue in male albino mice. Methods: A total of 30 male mice were divided into 3 groups. The first was a control group. The second group was subjected to crowding by cramming 20 mice in a small cage. The third group was fattened by eating a high-fat diet. Morphometric cells and histological measurements of the seminiferous tubule diameter, epithelium thickness, and Sertoli and Leydig cell counts were taken. Results: The crowding group testes showed the presence of necrosis and degeneration of spermatocytes, Sertoli, and Leydig cells. The obese group’s spermatocytes, Sertoli, and Leydig cells had shown severe necrosis, degeneration, and giant cell invasion. Histomorphometric measurements of seminiferous tubule diameter, epithelium-thickness, and Sertoli and Leydig cell counts revealed a considerable reduction in the obese group compared to the other groups. Furthermore, in the crowding and fattening groups, measurements of oxidative stress indicators revealed a decrease in glutathione value in the obese group compared to the control, whereas malondialdehyde rose in the overcrowded and obese groups compared to the control. The results of the immunohistochemical expressions for tumor necrosis factor-α (TNF-α) in the testes of mice revealed weak TNF-α positive expression in the control group, moderate expression in the crowding group, and strong expression in the obesity group. Conclusion: The study suggests that both obesity and crowding can impair testicular function, with obesity having the most significant impact. More research into the mechanisms underlying these effects, as well as potential interventions to improve testicular function in obese or overcrowded animals, is required.