Person-organization fit (P-O fit) refers to how well employees feel they match their organization in terms of values, goals, needs, and personal characteristics. Although previous research has primarily focused on the relationship between P-O fit and performance measures, increasing attention has recently been devoted to its potential role in employee mental health. The aim of this review was to summarize the current evidence regarding the relationship between P-O fit and mental health outcomes in occupational settings. The review was conducted in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 (PRISMA 2020) guidelines. Electronic searches were performed in the PubMed, Scopus, and EBSCO databases for studies published in 2016–2026. Studies were included if they examined the relationship between P-O fit and mental health outcomes among working populations. After the screening and eligibility assessment process, 16 empirical studies were included in the review. The reviewed studies included predominantly cross-sectional designs, although 2 longitudinal studies were also identified. Most studies showed that higher levels of P-O fit were associated with lower levels of stress, burnout, depressive and anxiety symptoms, and better well-being outcomes. Similar associations were reported in different occupational groups and countries. In conclusion, the findings suggest that congruence between employees and their organizational environments may play an important role in employee mental health. However, this review has several limitations, including the predominance of cross-sectional studies. Further longitudinal research is needed to clarify the relationship between P-O fit and employee mental health. Int J Occup Med Environ Health. 2026;39(4)