The effects of urbanization on the health of city dwellers have spurred research on the health-promoting benefits of forest exposure, and potential health-promoting benefits of human-nature relationships. In this meta-analysis, meta-regression, and systematic review, we aimed to analyze how forest-based interventions improved overall well-being through psychological and physiological changes by examining psychological scores and biomarkers. In December 2021, systematic searches were conducted on bibliographic databases (PubMed, Embase, and Cochrane) for studies involving psychological scores and physiological indicators. Data from 17 studies with 1418 participants showed that psychological symptoms (anxiety, depression, anger, fatigue, confusion, vigor), systolic blood pressure (BP), and malondialdehyde levels significantly improved in the forest-exposed group compared to in the nonexposed group, with high heterogeneity (I² = 66%–93%). Well-being-related psychological symptoms (friendliness, well-being, attention deficit hyperactivity disorder, self-esteem) and physiological markers (diastolic BP and cortisol) exhibited better tendencies in the forest-exposed group, with high heterogeneity (I² = 16%–91%), and meta-regression showed that moderators (age, country group, number of participants, study design, female participation rate, BMI) were significantly associated with forest-related therapeutic effects. In conclusion, forest visits have health-promoting effects that reduce the incidence of stress and lifestyle-related diseases, and are positively associated with psychological and physiological health.