A methanol extract of the twigs of Cinnamomum cassia was found to possess inhibitory activity against tyrosinase. Purification of the MeOH extract afforded four new phenolics, cassiferaldehyde (6), icariside DC (9), cinnacassinol (10), and dihydrocinnacasside (13), together with 10 known compounds (1-5, 7-12, and 14). The structures of the new compounds were determined by spectroscopic data interpretation. Compounds 1-6 and 8-13 showed strong inhibitory activity against tyrosinase, with IC(50) values ranging from 0.24 to 0.94 mM.