The genus Leonotis has 12 species widely distributed in tropics. Leonotis nepetifolia is economically important and has many medicinal uses. It is used against kidney diseases, rheumatism, dysmenorrhoea, bronchial asthma, fever and diarrhea. In this study the GC-MS analysis of Leonotis nepetifolia oil revealed the presence of 22 components. The major constituents of the oil are: 9-octadecenoic acid (Z)-, methyl ester (35.40%); 6-octadecynoic acid, methyl ester (22.68%); 9, 12-octadecadienoic acid (Z, Z)-, methyl ester (15.59%) and hexadecanoic acid, methyl ester (14.44%). The oil was evaluated for antimicrobial activity via the agar diffusion bioassay against five standard pathogenic microbes. The oil showed significant activity against Pseudomonas aeruginosa and partial activity against Staphylococcus aureus. In the DPPH assay the oil exhibited moderate free radical scavenging capacity.