The invention relates to the use in a cosmetic composition of an extract of the alga Phaeodactylum tricornutum, as a depigmenting active agent intended in particular for attenuating or eliminating skin pigmentation marks or for lightening the complexion or bodily hairs or head hair. The extract is preferably a lipid extract. The invention also relates to a cosmetic care method for attenuating or eliminating skin pigmentation marks or for lightening the complexion or bodily hairs or head hair, characterized in that it comprises the application, to at least one concerned area of the skin, of a cosmetic composition containing this extract.
