Microplastics (MPs) — grit-sized (5 mm or smaller) plastic particles — have recently been identified as ubiquitous and global contaminants in both freshwater and marine ecosystems, contributing to the ongoing decline of biodiversity in aquatic environments. Fish, as key players in pelagic food webs, are most likely to be exposed to MPs through ingestion, gill absorption and trophic transfer. This review synthesizes the available evidence of how MPs affect fish reproduction across multiple mechanisms: (i) gonadal toxicity and histopathological changes, (ii) endocrine disruption at the hypothalamic–pituitary–gonadal (HPG) axis, (iii) sperm quality and female fecundity effects, (iv) embryonic development and larval survival effects, (v), neuroendocrine-mediated behavioral effects on courtship, mate choice, and spawning, and vi transgenerational/epigenetics. The main molecular mechanisms include: oxidative stress induced by increased production of reactive oxygen species (ROS), dysregulated expression of steroidogenic genes, inhibition of vitellogenin (VTG) synthesis, disruption of GnRH–LH–FSH signaling pathway and epigenetic changes such as DNA methylation alteration. Model species (e.g., zebrafish, Danio rerio, Japanese medaka, Oryzias latipes, marine medaka, Oryzias melastigma) have yielded mechanistic insight and field studies across the commercial and ecologically important teleosts bolster ecological relevance. Parental exposure to MPs effect transfer of reproductive damage across generations (F1 and possibly F2) via epigenome reprogramming in gametes, leading to serious population-level conservation implications. We identify major gaps in knowledge, specifically with regard to nanoplastics, mixture toxicity and multi-generational exposures at environmentally realistic concentrations, and outline areas where future research is needed to support or redirect regulatory frameworks. (Liu et al., 2024, Wang et al., 2023)