This paper describes histological findings in the liver of Lutjanus guttatus after an acute mortality event in fish cultivated by river fishermen from Colima, Mexico, who were making their first attempt to cultivate this species. During 187 days, divided into two stages, 20,000 juveniles (6 g) were randomly distributed in three floating cages (125 m3). During the first 110 days (pre-fattening), the fish were fed commercial feed. From days 111 to 180 (fattening), the fish were given a test feed, high in fat (20.4%) and low in protein (30.2%). At the end of the first stage, the fish showed good biometric parameters as well as normal behavior and healthy appearance. During the second stage, starting on day 175, a strange behavior was observed followed by an acute mortality event; this alarmed the group of fishermen, who requested our intervention. In the necropsy and the histopathological analysis, the liver of the fish showed clear evidence of hepatocellular steatosis, possibly as a result of the nutritional stress to which they were subjected during cultivation. The present work can serve as a basis for future research, given the scarce information of this pathology in this fish species.