Shantanu kale, Kapil Kulkarni, Khanderao Jadhav Cosmos Sulphurus(Asteraceae) flowers commonly known as Sonkusum flowers were explored to find flavonoids, so, thin layer chromatography was performed and some of the flavonoids were identified.The reported flavonoids were known to have sunscreen activity and hence SPF factor of the dried flower extract (aqueous) was incorporated in topical formulation and evaluated in vitro with the help of Optometric Model-290 SPF.. The aqueous extract prepared from flower of cosmos sulphurus was used for Thin Layer Chromatography and then into topical formulation. In vitro determination of SPF was done with the help of method specified by The Comité de Liaison de la Parfumerie in Europe (COLIPA). The SPF was found to be 1.93 and Boots Star rating as 3, indicating that Cosmos Sulphurus(Asteraceae) flower extract (aqueous) can be considered as good candidate for Sunscreen or as an additive in any other sunscreen formulation. International Journal Of Pharmacy 2249-1848 2014-07-01 3 174-181 Copyright (c) Pharma Scholars. All rights reserved 2013