This paper investigates the occurrence of marine straminipilous organisms, primarily Halophytophthora, on decaying leaves of Rhizophora spp. fallen senescent mangrove leaves collected from Manila Marina Baytown Access Road and Boac, Marinduque. This was limited to the isolation and identification of Halophytophthora spp. and other marine stramenopiles present in collected mangrove leaves from Manila Marina Baytown Access Road and Boac, Marinduque Province. Collection of plant sample, preparation of culture media, isolation and identification were conducted. Various culture media and isolation techniques had been employed. Three Halophytophthora species were isolated from Boac, Marinduque using corn meal agar.