Two new drimane-type sesquiterpenes, cinnamadin (1) and cinnamodial 11alpha,12beta-dimethyl acetal (2), together with pereniporin B (3), ugandensolide (4), polygodial (5), capsicodendrin, cinnamodial (6), sitosterol, stigmasterol, lignoceric acid, cinnamosmolide (7), D-mannitol, and delta-tocotrienol were isolated from Cinnamosma madagascariensis. The structures of the new compounds were determined by physical, chemical, and spectroscopic evidence. Compound 7 and D-mannitol were isolated in high yield (5% and 1.36%, respectively). Evaluation of the alpha-glucosidase inhibitory properties of the isolated metabolites demonstrated that compounds 1 and 4 show moderate effects, while cinnamodial (6) exhibited the most potent activity. The chemosystematics of Cinnamosma species are also discussed.