The present work studied the cytogenetic and testicular damage induced by the antiarrhythmic drug rytmonorm (RT) and the protective role of grapefruit juice in albino rats. Treating rats with RT (13.5mg/Kg bodyweight) for five weeks caused a significant increase in the percentage of chromosomal aberrations either structural or numerical and decrease the mitotic index. Using comet assays, RT caused DNA fragmentation in the lymphocytes. Testis of RT treated rats showed many histopathological and morphometric alterations. In addition, the number of sperm head abnormalities was increased. Treating animals with RT and grapefruit juice (27ml/Kg bodyweight) led to an improvement in chromosomal aberrations, mitotic index, DNA damage, and testicular alterations caused by RT. In conclusion, the results of this study indicated that grapefruit juice showed a protective effect on cytotoxicty and testicular alterations induced by RT in albino rats and this is may be due to its potent antioxidant effects.