Crude extracts from different parts (leaf, bark and seed) of Swietenia mahagony (Family: Meliaceae) were screened for their antibacterial activity against 4 Gram positive and 8 Gram negative bacteria. Disc diffusion technique was used for in vitro screening. Among the crude extracts, chloroform and ethyl acetate extracts of leaf and bark showed good activity against all the tested organisms. The chloroform and ethyl acetate extracts of seed exhibited little or positive effect against most of the tested bacteria. The activities were compared to a standard antibiotic-kanamycin. Cytotoxic activity of crude extracts were determined using brine shrimp lethality bioassay and standard vincristine sulphate was used as positive control. The chloroform extract of seed and ethyl acetate extract of bark showed good cytotoxic activities and the LC50 values were found 13.75 and 11.64 microg mL(-1), respectively.