Simple SummaryPublic concern regarding environmental contaminants (ECs)-related reproductive disorders has increased due to increasing global rates of infertility. All kinds of ECs are on rise rapidly in developing and industrializing low- and middle-income countries. The aquatic environments throughout the world are repositories for enormous amounts of ECs. As the biology of the reproductive system is highly conserved in vertebrates, wildlife or laboratory studies on fish provide significant information to establish a detailed risk assessment, and to identify novel or more sensitive endpoints for ECs-related reproductive disorders. The adverse effects of ECs on endocrine regulation of reproduction in male fishes have been extensively studied and reviewed; however, our knowledge on the effects and mechanisms of action of ECs on determinants of male fertility is limited. The present study is a state-of-the-art comprehensive review on the ECs-related fertility threat in male fishes with emphasis on the ECs effects on sperm production, morphology, genome, and motility kinetics. After a brief introduction to reproductive biology, fertility indicators, and determinants of fertility in male fishes, wildlife evidences for reproductive disorders were reviewed in fishes from the polluted aquatic environment. The laboratory studies show that ECs detected in aquatic environment are capable of causing fertility threat at environmentally relevant concentrations associated with a decrease in fertility determinant(s). This study suggests an urgent need to better elucidate mechanisms through which ECs affect sperm functions to cause fertility threat.Increasing global rates of diminished fertility in males has been suggested to be associated with exposure to environmental contaminants (ECs). The aquatic environments are the final repository of ECs. As the reproductive system is conserved in vertebrates, studies on the effects of ECs on fertility endpoints in fishes provide us with valuable information to establish biomarkers in risk assessment of ECs, and to understand the ECs-related fertility threat. The aim of the present review was to evaluate associations between ECs and fertility determinants to better understand ECs-related male fertility threat in male fishes. Wildlife studies show that the reproductive system has been affected in fishes sampled from the polluted aquatic environment. The laboratory studies show the potency of ECs including natural and synthetic hormones, alkylphenols, bisphenols, plasticizers, pesticides, pharmaceutical, alkylating, and organotin agents to affect fertility determinants, resulting in diminished fertility at environmentally relevant concentrations. Both wildlife and laboratory studies reveal that ECs adverse effects on male fertility are associated with a decrease in sperm production, damage to sperm morphology, alternations in sperm genome, and decrease in sperm motility kinetics. The efficiency of ECs to affect sperm quality and male fertility highly depends on the concentration of the contaminants and the duration of exposure. Our review highlights that the number of contaminants examined over fertility tests are much lower than the number of contaminants detected in our environment. The ECs effects on fertility are largely unknown when fishes are exposed to the contaminants at early developmental stages. The review suggests the urgent need to examine ECs effects on male fertility when a fish is exposed at different developmental stages in a single or combination protocol. The ECs effects on the sperm genome are largely unknown to understand ECs-related inheritance of reproductive disorders transmitted to the progeny. To elucidate modes of action of ECs on sperm motility, it is needed to study functional morphology of the motility apparatus and to investigate ECs-disrupted motility signaling.