Objectives. To examine the association of Fit2Lead, an afterschool park-based youth mental health promotion program, and neighborhood juvenile arrests (2015-2017) in Miami-Dade County, Florida. Methods. We tracked juvenile (ages 12-17 years) arrest rates over 2 years of program implementation across zip codes matched by (1) park and (2) baseline sociodemographics and youth arrests. Fit2Lead mental and physical health, meditation, resilience, and life skills activities were offered in 12 high-need areas for youths (n = 501) aged 12 to 17 years. We tested the association of Fit2Lead implementation (binary variable) and change in juvenile arrest rates by zip code, adjusting for area-level gender, age, race/ethnicity, single-parent households, and poverty. Results. Fit2Lead was offered in areas composed of 48% male youths, 60% Hispanics, 29% non-Hispanic Blacks, 33% single-parent households, and 33% of residents living in poverty. After covariate adjustment, zip codes with Fit2Lead implementation showed a significant mean reduction (P < .001) in youth arrests per 10 000 youths aged 12 to 17 years per year compared with zip codes without program implementation (b = -6.9; 95% confidence interval = -9.21, -4.65). Conclusions. Park-based programs may have the potential to promote mental health and resilience, and also to prevent violence among at-risk youths.