Oysters cultured in the Manila Bay, specifically in Cavite City; Naic, Cavite; and Obando, Bulacan, were surveyed for the occurrence of Perkinsus sp. for three months from June to August 2012. Ray’s fluid thioglycollate medium (RFTM) revealed the presence of Perkinsus sp. hypnospores in oyster tissues. Based from the hypnospores present, the infection rate was recorded highest in Obando, Bulacan, with 79.4%, followed by Naic, Cavite, with 66.1% and Cavite City with 62.8% as the lowest. Light infection intensity was likewise recorded highest in Obando, Bulacan, with 18.93, followed by Naic, Cavite, with 12.86 and Cavite City with 12.56 as the lowest in which no significant differences occurred across sites.