Synopsis Rosmarinic acid (RA) has a number of interesting biological activities, e.g. anti‐viral, anti‐bacterial, anti‐inflammatory and antioxidant. The antioxidant activity of RA is stronger than that of vitamin E. Despite its strong antioxidant activity, it was limited to use in cosmetics because of the low water solubility, discolouration and chemical instability. The purpose of this study was to prepare RA‐loaded polycaprolactone (PCL) microspheres using emulsion solvent evaporation method and characterize them with different surfactants used in the formation process. Finally, long‐term stability of RA was evaluated in the cosmetic formulation. As a result, PCL microspheres were found to be spherical in shape, with zwitterionic surfactant‐PCL particles being the smallest size distribution and highest entrapment efficiency of RA. Emulsions containing RA‐loaded PCL microspheres showed a better long‐term stability of the RA compared with those containing only RA. These results suggest that RA may be stably and efficiently encapsulated into polycaprolactone microspheres.