Abstract: Environmental estrogens, as typical endocrine-disrupting chemicals widely present in aquatic environments, can exert sustained effects on the growth, development, reproductive processes, immune function, and population structure of fish by disrupting endocrine homeostasis. This review systematically summarizes the research progress on the effects of environmental estrogens on fish growth and reproduction, focusing on aspects such as reproductive physiology and sex differentiation, expression and regulation of development-related genes, changes in immune function, and population-level responses. Available studies have shown that environmental estrogens can interfere with gonadal development and sex differentiation by regulating the expression of estrogen receptors, vitellogenin, and genes involved in sex hormone synthesis. They can also alter immune cell activity, thymus development, and the expression of immune-related factors, thereby impairing immune defense capabilities in fish. At the population level, environmental estrogens may lead to skewed sex ratios, reduced fecundity, abnormal behaviors, and population decline. However, research on long-term low-concentration exposure, combined exposure to multiple pollutants, and transgenerational effects remains relatively insufficient, and the underlying mechanisms and associated ecological risks warrant further investigation. Looking ahead, the regulatory networks underlying the multilevel responses of fish to environmental estrogens—from the molecular and individual levels to the population level would be elucidated, by integrating multi-omics analyses, long-term exposure experiments using ecologically relevant concentrations, and multigenerational tracking. Thus, this work would provide a theoretical foundation and practical guidance for ecological risk assessment of environmental estrogens, pollution control in aquatic environments, and the conservation of fish resources and sustainable aquaculture.