Neighborhood research has increasingly emphasized the potential for contextual characteristics to moderate the effects of youths' experiences on their outcomes. Drawing on collective efficacy theory, we examine the variable consequences of youths' exposures to life-threatening violence across neighborhoods. We argue that strong community normative orientations supporting the control of violence diminish the negative effect of exposure to severe violence on subsequent mental health among urban youth. We also consider the extent to which the consequences of exposure to violence vary by gender. Employing data from the Project on Human Development in Chicago Neighborhoods, we estimate a series of multivariate, multilevel linear models of internalizing and externalizing symptoms. Results indicate that, for girls, exposure to life-threatening violence (witnessing someone being attacked with a weapon or shot) increases both internalizing and externalizing symptoms. However, this effect achieves statistical significance only for girls who reside in neighborhoods with lower collective efficacy. For boys, our analyses offered weaker evidence of violence exposure effects on mental health. Implications for research on the social context of mental health are discussed.