Dry roots of the plant Piper longum were extracted with n-hexane. The constituents were isolated and purified by column chromatography. The structures of the isolated constituents were confirmed by spectral analysis. The isolated constituents and n-hexane extract were found to show varying degree of antibacterial activity against all the tested bacteria. However, the aqueous extract did not show antibacterial activity against the tested bacteria. The isolated constituents were found to show better activity profile than the n-hexane extract, which indicates that the isolated constituents might be responsible for the antibacterial activity. The Minimum Inhibitory Concentration (MIC) value of piperine against Bacillus cereus and Escherichia coli was found to be 12.5 mg mL^-1.