Objectives. To evaluate whether the Operation Peacemaker Fellowship, an innovative firearm violence-prevention program implemented in Richmond, California, was associated with reductions in firearm and nonfirearm violence.Methods. We compiled city- and jurisdiction-level quarterly counts of violent firearm and nonfirearm incidents from statewide records of deaths from and hospital visits for homicide and assault (2005-2016) and from nationwide crime records of homicides and aggravated assaults (1996-2015). We applied a generalization of the synthetic control method to compare observed patterns in firearm and nonfirearm violence after implementation of the program (June 2010) to those predicted in the absence of the program, using a weighted combination of comparison cities or jurisdictions.Results. The program was associated with reductions in firearm violence (annually, 55% fewer deaths and hospital visits, 43% fewer crimes) but also unexpected increases in nonfirearm violence (annually, 16% more deaths and hospital visits, 3% more crimes). These associations were unlikely to be attributable to chance for all outcomes except nonfirearm homicides and assaults in crime data.Conclusions. The Operation Peacemaker Fellowship may have been effective in reducing firearm violence in Richmond but may have increased nonfirearm violence.