Inhibition of fatty acid synthase (FAS) has been proposed to be a new therapeutic target for the treatment of cancer and obesity. In our preliminary screening study on the FAS inhibitory activity, a n-hexane soluble fraction prepared from the fruit of Schisandra chinensis (Schisandraceae) was found to inhibit FAS activity at 100 microg/mL. Nine dibenzocyclooctadiene lignans were isolated from the active fraction and were evaluated for their inhibitory effect on FAS for the first time. The compounds possessing a benzoyl or tigloyl group in the dibenzocyclooctadiene skeleton entirely inhibited the FAS activity in a dose dependent manner. The findings may be partially related to the anticancer effect of the medicinal plant, suggesting a further study on the anticancer potential of dibenzocyclooctadiene derivatives.