<p>Infection of plants with molds and inadequate storage conditions of plant materials contribute to contamination of crops like cereals, corn and soybeans with mycotoxins. Plant-derived ingredients serve as major protein sources in aquaculture feeds; however, the increasing use of insects as alternative nutrient sources introduces additional potential pathways for mycotoxin contamination. Strong evidence shows that exposure of fish to mycotoxins can negatively affect their health, leading to reduced growth, impaired immune response and reproductive disorders. However, knowledge of the effects of mycotoxins on farmed insects is still limited. Little is known about the insect metabolism of mycotoxins and their transfer to animal feed, which constitutes a weakness of safety assessments of insects as feed components. This review provides comprehensive information about the consequences of mycotoxin contamination of feed materials and feeds used in aquaculture. To facilitate understanding of the problem and its scale, the mycotoxin levels in plant materials and finished feeds used in aquaculture were compiled and analyzed together with the contamination levels of fish-derived food. Moreover, the available data on the effects of fish exposure to the selected mycotoxins are summarized, highlighting the complexity of the biological activity of these compounds. Finally, recent challenges to the safety of using insects as a protein source in fish nutrition are discussed. The information provided herein is important for assessing the health and economic risks of the growing use of modern feed ingredients in the sustainable aquaculture.</p>