The Syrian hamster (Mesocricetus auratus) has been extensively used as an animal model to investigate neuronal networks underlying various behaviors where 5-HT_3A receptors have been found to play a critical role. To date, however, there is no comprehensive description of the distribution of 5-HT_3A receptors in the Syrian hamster brain. The current study examined the localization of 5-HT_3A receptors across the neuraxis of the Syrian hamster forebrain using immunohistochemistry. Overall, 5-HT_3A receptors were widely and heterogeneously distributed across the neuraxis of the Syrian hamster brain. Notably, the most intense 5-HT_3A immunolabeling patterns were observed in the cerebral cortex and amygdala. In addition, high variability in receptor density and expression patterns (i.e., perikarya, fibers and/or neuropilar puncta) was observed within the majority of brain areas examined, indicating that the role this receptor has in the modulation of a particular neural function differs depending on brain region. In some regions (i.e., nucleus accumbens) differences in the immunolabeling pattern between rostral, medial and caudal portions were also observed, suggesting functional heterogeneity of this receptor within a single brain region. Together, these results and the localization of this receptor to brain areas involved in the regulation of sexual behavior, aggression, circadian rhythm, drug abuse and anxiety implicate 5-HT_3A receptors in the modulation of various behaviors and neural functions in the Syrian hamster. Further, these results underscore the importance of evaluating 5-HT_3A receptors as a pharmacological target for the treatment of various psychopathological disorders.