The invention relates to a cosmetic composition comprising the following as active agents: a first active agent consisting of an amber extract, and at least one other cosmetically active agent selected from the group consisting of extracts of Bertholletia excelsa, extracts of Potentilla erecta, magnesium aspartate, peptides acting on muscle contraction, particularly acetyl hexapeptide 3, peptides and their derivatives grafted with a fatty acid, particularly a C.sub.16 fatty acid, promoting collagen synthesis, particularly palmitoyl oligopeptide pentapeptide 3 or palmitoyl tetrapeptide 7, soy flour hydrolyzates and plant glycolipids, particularly cereal glycosphingolipids and more particularly wheat glycosphingolipids. It further relates to the use of an amber extract as a cosmetic agent acting on the dermal supporting proteins and/or the enzymatic systems that degrade the dermal proteins and/or the glycan-type essential components of the extracellular matrix, particularly proteoglycans, for improving the essential biomechanical properties of the skin, namely firmness and elasticity, in the preparation of a cosmetic composition.