Marine algae are widely used as cosmetics raw materials. Likewise, freshwater alga Cladophora glomerata may be a good source of fatty acids and others bioactive agents. The aims of this study was to find out if the addition of the extract from the freshwater C. glonerata affects the stability of prepared cosmetic emulsions and to investigate in vivo effects of the extract in cosmetic formulations on hydration and elasticity of human skin. Extract from the freshwater C. glonierata was obtained using supercritical fluid extraction (SFE). Two forms of O/W emulsions were prepared: placebo and emulsion containing 0.5% of Cladophora SFE extract. The stability of obtained emulsions was investigated by using Turbiscan Lab Expert. Emulsions were applied by .volunteers daily. Corneometer was used to evaluate skin hydration and cutometer to examine skin elasticity. Measurements were conducted at reference point (week 0) and after 1st, 2nd, 3rd and 4th week of application. The addition of Cladophora extract insignificantly affected stability of the emulsion. The extract from C. glomerata in the emulsion influenced the improvement of both skin hydration and its elasticity. Thus, freshwater C. glonierata extract prepared via SFE method may be considered as an effective cosmetic raw material used as a moisturizing and firming agent.