Toxocara canis is widely distributed parasite that not only presents in definitive hosts but also occurs in paratenic hosts including human. Larvae migrate throughout the somatic tissue causing severe inflammatory and pathological reactions. This study aims to detect the effect of infection with Toxocara canis on testis of rats regarding histopathological, histochemical and immunohistochemical changes and amelioration of these changes with either vaccination with gamma radiation-attenuated embryonated eggs or with herbal treatment with thyme. The study was conducted on eighty rats classified into four groups (20 each): Group A (normal control); Group B (infected control); Group C infected and treated with thyme oil (thyme-treated); and Group D vaccinated with 800 Gy gamma radiation-attenuated embryonated eggs, and challenged with the same number of eggs (vaccinated-challenged). Testicular tissues were stained with Haematoxylin and Eosin (H &E) for histopathological study. Periodic acid Schiff’s (PAS), bromophenol blue (BPB) and Feulgen’s reaction for carbohydrates, proteins and DNA, respectively were done to examine histochemical changes. Immunohistochemical study was done through expression of TGF-β1 and caspase-3. Infected control group B showed severe histopathological changes with marked decrease in PAS +ve materials, total proteins and DNA and enhanced expression of Transforming growth factor- β1 (TGF-β1) and caspase-3. Moderate changes were observed in testicular tissues of group C treated with thyme. Slight changes were detected in vaccinated-challenged group D. It was concluded that Toxocara canis infection causes marked hispathological, histochemical and immunohistochemical changes in testicular tissues of rats that can be ameliorated by vaccination with radiation-attenuated infective stage or treated with thyme; however vaccination is more effective in protection.