Distribution of firearm victimization is not equal within cities. Victimization can persistently concentrate in a small number of neighborhoods, while others experience very little violence. Theorists have pointed to one possible explanation as the ability of groups to control violence using social capital. Researchers have shown this association at the U.S. county, state, and national levels. Few studies, however, have examined the relationship between neighborhood social capital and violence over time. This study uses longitudinal data to ask whether neighborhood social capital both predicts and is influenced by firearm victimization over 3 years in Philadelphia. The results of several regression analyses suggest that trusting others and firearm victimization are inversely related over time. Implications for neighborhood policy planning and social capital as a theoretical framework are discussed.