Cardicola nonamo n. sp. (Digenea: Aporocotylidae) infects the heart of white seaperch, Phanerodon furcatus Girard, 1854 (Perciformes: Embiotocidae) (type host), in Monterey Bay, California, and the branchial vessels of rubberlip seaperch, Rhacochilus toxotes Agassiz, 1854 (Embiotocidae), from Naples Reef, Santa Barbara Channel, off Santa Barbara, California. It is most easily distinguished from other species of Cardicola Short, 1953 by the combination of having (1) rows of minute tegumental spines distributing along the entire ventrolateral body margin; (2) an aspinous anterior sucker comprising a nearly indistinct spheroid structure centering on the mouth; (3) an esophagus 17–21% of the total body length; (4) convoluted posterior ceca 51–65% of the total body length and 9–18× length of the anterior ceca; (5) a rectangular, intercecal testis not extending posteriad beyond the posterior ceca; (6) a post-testicular and post-cecal ovary; (7) an oviduct emanating from the posterodextral margin of the ovary; (8) a post-ovarian uterus coiling twice just posterior to the ovary; and (9) male and female genital pores opening dorsomedially and posterior to the uterus and ootype. The new species most closely resembles Cardicola ambrosioi Braicovich, Etchegoin, Timi, and Sardella, 2006, which infects the blood vessels of the gill and liver of Brazilian flathead, Percophis brasiliensis Quoy and Gaimard, 1825 (Perciformes: Percophidae), in the southwestern Atlantic Ocean off Argentina; however, C. ambrosioi differs morphologically from the new species at least by lacking post-ovarian spine rows and by having posterior ceca that are 4× length of the anterior ceca. This is the first published record of an aporocotylid from a surfperch (Embiotocidae) as well as that of a species of Cardicola from the Pacific Ocean east of the Hawaiian Islands.