The heart and gill of 125 spotted seatrout, Cynoscion nebulosus (Cuvier, 1830), (Perciformes: Sciaenidae) from 5 Gulf of Mexico localities (Mississippi Sound [n  =  18] [30°23′21″N; 88°51′44″W], Apalachicola Bay [n  =  17] [29°40′18″N; 85°00′09″W], Suwannee Sound and Wacasassa Bay [n  =  22] [29°7′55″N; 83°2′24″W], Tampa Bay [n  =  58] [27°41′58″N; 82°37′49″W], and Charlotte Harbor [n  =  10] [26°43′07″N; 82°11′27″W]); 40 spotted seatrout from 2 northwestern Atlantic Ocean localities (St. John's River Estuary [n  =  28] [30°22′29″N; 81°34′08″W] and Indian River Lagoon [n  =  12] [28°5′31″N; 80°36′08″W]); and 103 sand seatrout, Cynoscion arenarius Ginsburg, 1930, from 2 Gulf of Mexico localities (Mississippi Sound [n  =  102] and Tampa Bay [n  =  1]) were examined for the presence of fish blood flukes (Digenea: Aporocotylidae). One adult aporocotylid was collected from the heart of each infected spotted seatrout captured in Tampa Bay (6 of 58 infected, 10%) and St. John's River Estuary (1 of 28 infected, 4%) as well as from the heart of the single sand seatrout from Tampa Bay. We identified these aporocotylids as Cardicola laruei Short, 1953, based on light and scanning electron microscopy that matched them to the original species description of C. laruei, the type specimens in the United States National Parasite Collection (holotype USNPC 37377; paratypes USNPC 37378–9), and other of Short's original specimens now in our own collection. The present study is the first reported collection of this aporocotylid (i) from Tampa Bay, (ii) from the Atlantic Ocean, (iii) from the heart of spotted seatrout, and (iv) since its original description in 1953. Among other significant morphological features previously not ascribed to C. laruei, these specimens have a spheroid anterior sucker with concentric rows of minute spines anterior to the mouth. The fully developed, spindle-shaped egg of C. laruei embeds in the gill epithelium of its fish host proximal to the afferent branchial arterioles and encloses a ciliated miracidium. This report significantly contributes to our knowledge of C. laruei by (i) extending its known geographic distribution to a new ocean basin (Atlantic Ocean), (ii) adding supplemental morphological data derived from light and scanning electron microscopy, (iii) providing the first published observations of nonadult life history stages (egg and miracidium), and (iv) confirming that sympatric, congeneric seatrouts are infected by C. laruei.