: Cyanotoxins are the metabolites of cyanobacteria, belonging to different chemical groups and of diverse mechanisms of toxicity. Generally, they are divided into hepatotoxins, neurotoxins and dermatotoxins/irritant toxins. There is a growing evidence, that besides the above mentioned toxicity, exposure to cyanotoxins may also induce other effects, among others the disruption of neuroendocrine and immune systems. The purpose of that paper is to sum up the current information obtained from the literature and from our own studies about the influence of cyanohepatotoxins on neuroendocrine and immune systems of fish. From the presented data it appears, that microcystins, nodularin and cylindrospermopsin, except for their hepatotoxic activity, are potent to exert such effects as HPI axis activation resulting in physiological and behavioural changes, disturbances in thyroid hormones release/metabolism, as well as impairment of immune responses in fish. However the studies in that area are still incomplete and many questions remain to be answered, especially what consequences for fish population health status it brings.