The genotoxicity of the ethanolic extract of betel nut was evaluated using sarcoma 180 tumour bearing mouse considering sperm motility, sperm viability, biochemical estimation of fructose in seminal fluid and sperm head morphology assays. Sperm head morphology was studied by H-E staining and Toluidine blue staining method. But Toluidine blue staining method is a reliable method to evaluate the DNA damage of sperms. Ethanolic BNE (betel nut extract) can suppress the percentage of sperm motility, sperm viability and seminal fructose level. In addition, it can also enhance the percentage of DNA damaged sperms. Moreover, histological sections of testes have been studied in control and BNE treated sarcoma 180 tumour bearing mice to highlight the potential toxic effect of BNE. The significant decreasing rate of seminal fructose concentration, sperm motility as well as viability and increasing rate of sperm head abnormality in different doses of treated series may be as a result of different toxic alkaloid ingredients present in BNE. Therefore, the results showed the potential of the BNE to induce different types of germ cell abnormalities in tumour bearing male mice.