Marine algae are rich sources of bioactive compounds capable of harboring secondary metabolites which are structurally and biologically active. In our study, the methanolic extract of marine algae Caulerpa racemosa (green algae) was employed to determine the antibacterial and larvicidal activity. The antibacterial activity showed effective inhibition against five pathogenic bacteria. A significant zone size of 16mm was observed for Pseudomonas aeruginosa. The methanolic extract of Caulerpa racemosa showed effective larvicidal activity against Culex tritaeniorhynchus and the histopathological studies revealed the rupture in mid gut of larvae. The bioactive compounds in the crude extract were further identified as 2-(-3-bromo-1-adamantyl) acetic acid methyl ester and Chola-5, 22-dien-3-ol by GC-MS. Hence the bioactive compounds obtained from the methanolic extracts could be used for the bactericidal and larvicidal activity which will overcome the harmful impact of synthetic insecticide on environment. © 2014 Higher Education Press and Springer-Verlag Berlin Heidelberg.