This meta-analysis evaluates the effectiveness of positive psychology interventions (PPIs) in enhancing subjective well-being, psychological well-being, and reducing depressive symptoms. A systematic review of 40 studies involving 6,139 participants found small but significant effects of PPIs. The standardized mean differences were 0.34 for subjective well-being, 0.20 for psychological well-being, and 0.23 for depression. These effects were sustained at follow-up, though heterogeneity among studies was high. Factors such as longer intervention duration, individual delivery, and referral from healthcare professionals were associated with greater effectiveness. Publication bias was indicated, and study quality varied. The results suggest that PPIs can improve well-being and reduce depressive symptoms, but more high-quality studies are needed to strengthen evidence. The study highlights the importance of considering intervention type, duration, and quality in future research. Positive psychology interventions, particularly self-help formats, show promise for mental health promotion and prevention, but further research is required to optimize their effectiveness.This meta-analysis evaluates the effectiveness of positive psychology interventions (PPIs) in enhancing subjective well-being, psychological well-being, and reducing depressive symptoms. A systematic review of 40 studies involving 6,139 participants found small but significant effects of PPIs. The standardized mean differences were 0.34 for subjective well-being, 0.20 for psychological well-being, and 0.23 for depression. These effects were sustained at follow-up, though heterogeneity among studies was high. Factors such as longer intervention duration, individual delivery, and referral from healthcare professionals were associated with greater effectiveness. Publication bias was indicated, and study quality varied. The results suggest that PPIs can improve well-being and reduce depressive symptoms, but more high-quality studies are needed to strengthen evidence. The study highlights the importance of considering intervention type, duration, and quality in future research. Positive psychology interventions, particularly self-help formats, show promise for mental health promotion and prevention, but further research is required to optimize their effectiveness.