Immigrant Mexican American (MA) youth are at greater risk for violence exposure due to risk factors associated with migration-postmigration processes and as they settle into urban U.S. communities marked by crime and poverty. Less is known about the contexts of this exposure. Specifically, what are the ecological contexts in which youth witness intimate partner violence (IPV), how do these experiences differ by immigration generational status, and what is the impact on youth's externalizing and internalizing behaviors? MA adolescents (N = 279; 15-17 years, M = 16.17, SD = 0.81) from the Southwest United States participated in an online survey. Over half of adolescents had witnessed at least one incidence of IPV in the prior 2 weeks, usually involving their peers. Adolescents who had spent more time in the United States were more likely to witness violence and rated it as more severe than more recently immigrated youth. A cross-sectional path model revealed that witnessing IPV was associated with internalizing and externalizing problems. However, the associations between witnessing IPV and dating violence perpetration and victimization were mediated through acceptance of dating violence norms. Each successive generation may be more likely to witness violence across a range of ecological contexts. Witnessing violence may be central to a host of negative outcomes, including deviancy, poor mental health, and dating violence. However, preventive interventions can help youth to challenge violence norms within intimate partnerships as well as to cope with violence in their homes, peer groups, and communities.