BACKGROUND: Postpartum period is a critical time that requires adjustments not only for mothers but also for fathers and may pose risk for depression. Studies show that the prevalence of paternal postpartum depression (PPD) is between 1.2% and 25.5%. PPD is an under-recognized public health issue and its reported influencing factors are still inconclusive. OBJECTIVE: The purpose of this paper is to extend the literature by examining influencing factors that affect paternal PPD and describe the strength their associations. METHODS: We conducted keyword search of Web of Science, PubMed, Embase, the Cochrane Library and PsycARTICLES electronic databases up to Jan 17, 2020, without language restrictions, for observational studies investigating the factors influencing paternal PPD and its effects. Fixed or random effect model was used to pool odds ratio (OR) and 95% confidence intervals (CI) with Stata software 12.0. Heterogeneity between studies was evaluated using Cochran's chi-squared test (Cochran's Q) and I values. RESULTS: Nineteen cross-sectional studies and eighteen cohort studies published from 1996 to 2019 were included in this review and seventeen studies in the meta-analysis. Factors affecting paternal PPD can be classified into paternal, maternal, infant and family factors. In Meta-analysis, 9 of 17 influencing factors were revealed to be statistically significant: 1) paternal factors: unemployment OR= 2.59 (95%CI:1.42-4.74), low social support OR=1.05 (95%CI:1.03-1.08), negative life events OR=1.45 (95%CI:1.13-1.87), perceived stress OR=1.08 (95%CI:1.03-1.12), financial strain OR=2.07 (95%CI:1.13-3.81), history of mental illness OR=3.48 (95%CI:2.49-4.86); 2) maternal factors: parity OR=1.36 (95%CI:1.13-1.65) and maternal postnatal depression OR=1.17 (95%CI:1.03-1.33); 3) family factors: low marital satisfaction OR=1.40 (95%CI:1.22-1.61). No statistically significant association with infant factors was found in the meta-analysis. LIMITATIONS: There was publication bias since we only included English studies. Samples were under-represented in low-and middle-income countries. The meta-analysis results are subject to unobserved confounding factors and cannot explain causality. CONCLUSION: This overview of the evidence suggests a relationship between paternal employment, psychological status, history of maternal mental illness, first pregnancy, marital relationship and paternal PPD. The low number of studies for some infant factors in meta-analysis leaves gaps in knowledge that need to be addressed. The mechanisms underlying the reported associations and their causal relationship still remain unclear. The awareness of the serious long-term consequences of paternal PPD should encourage better identification of those at risk and the development of effective interventions to protect fathers from PPD.