The present invention pertains to a moisturizing cosmetic composition comprising a galacto-oligosaccharide that consists of 4 to 10 monosaccharide units and has at least one fructose residue. This galacto-oligosaccharide may be obtained from a plant belonging to the Lamiaceae family flora. The invention also pertains to a novel extract from this plant. This composition has a satisfactorily improved skin moisturizing effect without stickiness. Moreover, the galacto-oligosaccharide provides for a specific synergetic effect with polyhydric alcohols, resulting in a further increased skin moisturizing effect.