Until now studies in Brazil of the pathological action of Contracaecum sp. larvae in Hoplias malabaricus have been rare. The aim of the present study was to analyze and describe histopathological changes in the stomach of H. malabaricus caused by different intensities of infection by larvae of Contracaecum sp., and the hematological effects of such infection. The mean intensity of infection by L3 larvae of Contracaecum sp. correlated positively with Hematocrit percentage (Hct%) and correlated negatively with mean corpuscular volume (MCV). These findings are possibly related to the passage of larvae from the stomach to the mesentery, potentially due to hemorrhaging t. Fish with high infection intensity had larvae of Contracaecum sp in the submucosal of the stomach, which caused destruction of Type I and Type III collagen (finer and more delicate collagen fibers which do not form beams and are permeated by fundamental substances) around the parasite. Microscopic analysis showed that crypts were arranged regularly throughout the stomach mucosal, varying in number, size and depth, depending on the region of the stomach Ver menos