Abstract: The present investigation was undertaken to evaluate in vitro antimicrobial activity of Semecarpus anacardium L. (Anacardiaceae) nuts oils. Essential oil from nut of S. anacardium was extracted by hydro-distillation method in a Clevenger type apparatus. The antimicrobial screening of the isolated essential oil was performed against Gram positive-Bacillus subtilis (ATCC 6633), Staphylococcus aureus (ATCC 25923) Gram negative-Proteus vulgaris (ATCC 2027), Escherichia coli (ATCC 25922) and fungal strains Aspergillus niger (ATCC 16404), Aspergillus fumigates (ATCC 26933), Candida albicans (ATCC5027) and Candida glabrata (ATCC 66032) using disc diffusion method. The essential oil was found to be more or less active against almost all tested pathogenic strains with varied spectrum of inhibition zone (7.0±0.06-13.0±0.01 mm). The significant inhibitory effect was observed against Staphylococcus aureus (12.0±0.05 mm) and A. niger (13.0±0.01 mm). The significant potential of Semecarpus anacardium nut oil concludes that it could serve as a source of antimicrobial agents.