Testicular injury resulting from exposure to chemical agents and environmental pollutants is an increasingly important contributor to male infertility, particularly among individuals exposed to environmental toxicants, industrial contaminants, occupational chemicals, and chemotherapeutic drugs. Such injuries frequently lead to persistent impairment of spermatogenesis, hormonal dysfunction, and reduced reproductive capacity, while effective restorative treatment options remain limited. In recent years, gene therapy has emerged as a novel regenerative strategy capable of targeting the molecular pathways involved in toxicant- and environment-induced testicular damage. This systematic review aimed to evaluate the efficacy of gene-based interventions in restoring testicular function following injury induced by chemical and environmental exposures. A comprehensive literature search was conducted across PubMed, Scopus, Web of Science, Embase, and Google Scholar, covering studies published between 2000 and 2025. The search identified 1,254 records, of which 1,032 remained after duplicate removal. Following title and abstract screening and full-text assessment, 15 studies met the inclusion criteria and were included in the qualitative synthesis, comprising 12 animal studies and 3 human clinical studies. Across preclinical models, gene therapy was associated with significant improvements in testicular histology, spermatogenesis, and endocrine function. Treated animals demonstrated marked increases in sperm concentration (mean increase of approximately 4.2 × 10⁶/mL), improved sperm motility (25–40%), and restoration of serum testosterone levels to 80–95% of baseline values. Fertility restoration was reported in five animal studies, with successful pregnancy rates ranging from 60% to 85%. Antioxidant and anti-apoptotic gene constructs, particularly those targeting oxidative stress pathways activated by environmental toxicants, showed superior therapeutic effects. Human studies reported modest but clinically meaningful improvements in sperm parameters and hormonal profiles; however, direct fertility outcomes were not assessed. In conclusion, current evidence suggests that gene therapy holds substantial promise for restoring testicular function following damage induced by chemical and environmental exposures. Nevertheless, clinical data remain limited, underscoring the need for well-designed human trials with standardized outcome measures and long-term safety evaluation.