The essential oil from the aerial parts of Blumea lacera collected from Biratnagar, Nepal, has been obtained by hydrodistillation and analyzed by gas chromatography - mass spectrometry. The major component from the oil, (Z)-lachnophyllum ester, was isolated by preparative silica gel chromatography. B. lacera oil was dominated by (Z)-lachnophyllum ester (25.5%), (Z)-lachnophyllic acid (17.0%), germacrene D (11.0%), (E)-β-farnesene (10.1%), bicyclogermacrene (5.2%), (E)-caryophyllene (4.8%), and (E)-nerolidol (4.2%). Also detected in the oil were (E)-lachnophyllic acid (3.3%) and (E)-lachnophyllum ester (1.7%). (Z)-Lachnophyllum ester exhibited cytotoxic activity against MDA-MD-231, MCF-7, and 5637 human tumor cells, as well as antibacterial and antifungal activity.