ABSTRACT The fruits of guava, Psidium guajava L., Myrtaceae, are cultivated as food and used in agroindustries, generating byproducts or waste that represent environmental problems and require adequate destination. However, these byproducts present high levels of secondary metabolites and have been awakened interest regarding to its reusing. The extract was standardized in ellagic acid concentration by high performance liquid chromatography. The additivation capacity in the in vitro photoprotective efficacy of guava byproduct extract standardized in ellagic acid was verified as a result of its incorporation in cosmetic formulations, comparing it with a standard product. The extract presented synergy with the chemical UV filter (ethylhexyl methoxycinnamate), enhancing the solar protection factor of the phytocosmetic in 17.99%. Besides that, it was possible to show its antioxidant activity and the presence of secondary metabolites such as phenols and flavonoids. According to the results, it is possible to claim that the extract from the guava's agroindustrial byproducts present potential to be studied and reused, applying on the development of innovative products intended to the photoprotection care.