Crime is both a societal safety and public health issue. Examining different measures and aspects of crime-related safety and their correlations may provide insight into the unclear relationship between crime and children's physical activity. We evaluated five neighborhood crime-related safety measures to determine how they were interrelated. We then explored which crime-related safety measures were associated with children's total moderate-to-vigorous physical activity (MVPA) and MVPA in their neighborhoods. Significant positive correlations between observed neighborhood incivilities and parents' perceptions of general crime and disorder were found (r = 0.30, p = 0.0002), as were associations between parents' perceptions of general crime and disorder and perceptions of stranger danger (r = 0.30, p = 0.0002). Parent report of prior crime victimization in their neighborhood was associated with observed neighborhood incivilities (r = 0.22, p = 0.007) and their perceptions of both stranger danger (r = 0.24, p = 0.003) and general crime and disorder (r = 0.37, p < 0.0001). After accounting for covariates, police-reported crime within the census block group in which children lived was associated with less physical activity, both total and in their neighborhood (beta = -0.09, p = 0.005, beta = -0.01, p = 0.02, respectively). Neighborhood-active children living in the lowest crime-quartile neighborhoods based on police reports had 40 min more of total MVPA on average compared to neighborhood-active children living in the highest crime-quartile neighborhoods. Findings suggest that police reports of neighborhood crime may be contributing to lower children's physical activity.