Circadian rhythms are cyclic oscillations in the intensity of biological processes associated with the change of day and night, to which many organisms have adapted during evolution. Disturbances in circadian rhythms are caused by both environmental factors (e.g., changes in the time zone or length of day/night) and disrupted internal regulation of cycles (e.g., mutations of key clock genes). These changes can trigger pathogenesis of various diseases, including psychopathologies. Since the mechanisms underlying circadian regulation are rather evolutionarily conserved, experimental in vivo animal models are actively used to probe these processes and their relationship with psychopathologies. Here, we discuss the circadian rhythm regulation, as well as their cross-taxon similarities and differences between mammals and teleost fish (zebrafish, Danio rerio). We also discuss recent findings on molecular genetic mechanisms underlying the regulation of circadian rhythms and their link to the pathogenesis of mental disorders in humans and model organisms.