Background: To use a quantitative approach to examine the effects of family interventions on physical activity (PA) and sedentary behavior (SB) in children aged 2.5-12 years. Methods: PubMed, OVID, Web of Science, and others were searched from their inception to May 2020. Intervention studies that examined the effects of family interventions on PA among children aged 2.5-12 years were included in this meta-analysis. Lastly, subgroup analyses were conducted to examine the potential modifying effects of family intervention’s characteristics and study quality. Results: Eleven articles met the inclusion criteria for this review. Studies investigated a range of PA outcomes, including moderate-to-vigorous PA (MVPA), total PA (TPA), daily steps, and SB levels. Meta-analysis showed that family intervention had a significant effect on PA [standardized mean difference (SMD)=0.10; 95%CI=0.01, 0.19], especially for daily steps [weight means difference (WMD)=1,006; 95%CI=209, 1,803], but not for SB (WMD=-0.38; 95%CI=-7.21, 6.46). Subgroup analyses indicated the improvements in PA occurred when children were 6-12 years old, intervention focused on PA only, intervention duration ≤ 10 weeks, and “low risk of bias” study performed. Conclusions: Family intervention may be a promising way to promote children’s PA levels, especially for daily steps. Trial registration: Meta-analysis protocol was registered on PROSPERO: CRD42020193667.