Bromadialone is a member of coumarins which are widely used as an anticoagulant rodenticide for the eradication of rodents. This denotes a high possibility that they contaminated the diet of man and his farm animals and probably enter the food chain; this fact alarmed some scientists to study their biological influence. Origanum majorana is a natural herbal product used in the management of many diseases and is extensively studied for its ability to protect cells from damages. The present study was to evaluate to investigate some toxicological effect of the bromadialone on (chromosomes, liver, and testis) of albino male rat and marjoram, as well as the protective effect of aqueous extract of majorana leaves against bromadialone–induced mutagenic effect and histopathological effect on liver and testis. In this study, 65 adult male Wistar albino rats (Rattus norvegicus) were used and arranged in 13 different groups. Group (0) as control. Groups (1 and 2) were received Origanum majorana extract (150 mg/kg b.w. (1.5%) and 300 mg/kg b.w. (3%), respectively. Groups (3 and 4) received single dose (1/10 LD50) of bromadialone for group (3) and (1/20 LD50) for group (4). Groups (5, 6, 7, and 8) received bromadialone (1/10 LD50 and 1/20 LD50) then Origanum majorana extract (150 mg/kg b.w. (1.5%) and 300 mg/kg b.w. (3%), respectively. Groups (9, 10, 11, and 12) received Origanum majorana extract 150 mg/kg b.w. (1.5%) and 300 mg/kg b.w. (3%), then bromadialone (1/10 LD50 and 1/20 LD50), respectively. Animals from all above-mentioned groups were sacrificed, their bone marrow cells were analysed for chromosomal damages and specimens of tissues for histopathological examination of liver and testis. Bromadialone caused a significant increase of chromosomal aberrations and reduction of mitotic index value, bromadialone also had histopathological effects in internal organs (liver and testis).This work revealed that the antigenotoxic and anticytotoxic potential of Origanum majorana against bromadialone –induced more or less genotoxic, cytotoxic and histopathological effects in rat bone marrow cells, liver and testis, respectively.