Crime and safety are often cited as potential hurdles to park use and park-based physical activity. Using comprehensive data sources including both objective and subjective measurements at the park level and the individual level, this study aimed to assess the association between crime rates and use of local parks in low-income urban neighborhoods. The authors observed 48 parks and conducted local resident surveys in low-income neighborhoods in Los Angeles during a 2-year study period (2013-2015). Crime data were geocoded within a 1-mile radius of parks' addresses and longitudinal models were fitted to estimate the association between crime rates and park use outcomes in 2017. One gun-related violent crime per 10,000 people during the 6-month period prior to data collection was associated with an average of 13.5%-15.8% reduction in observed park use and park-based moderate to vigorous physical activity (p<0.05) in the 6-month observation period. The relationship was significant in seniors (33%-40% reduction) and adults (13%-18%), but insignificant for teenagers (2%-4%) and children (10%-12%). Homicide rates were also significantly related to lower self-reported park use (p<0.05). Gun-related violent crimes have relatively long-term negative associations with population health by reducing utilization of outdoor park space. There can be additional population health benefits from controlling and reducing gun-related violent crimes beyond immediate impacts on public safety and mortality.