Adolescent substance abuse is a serious public health concern, and in response to this problem, a number of effective treatment approaches have been developed. Despite this, retaining and engaging adolescents in treatment are 2 major challenges continuously faced by practitioners and clinical researchers. Low retention and engagement rates are especially salient for ethnic minority adolescents because they are at high risk for underutilization of substance abuse treatment compared to their White peers. Latino adolescents, in particular, are part of the fastest growing ethnic minority group in the United States and experience high rates of substance use disorders. Heretofore, the empirical examination of cultural factors that influence treatment retention and engagement has been lacking in the literature. The goal of this study was to investigate the influence of the cultural variables ethnic identity, familism, and acculturation on the retention and engagement of Latino adolescents participating in substance abuse treatment. This study used data collected from a sample of Latino adolescent males (N = 96), predominantly of Mexican descent, and largely recruited from the juvenile justice system. Analysis was conducted using generalized regression models for count variables. Results indicated that higher levels of exploration, a subfactor of ethnic identity, and familism were predictive of attendance and engagement. In contrast, higher levels of Anglo orientation, a subfactor of acculturation, were predictive of lower treatment attendance and engagement. Clinical implications for the variables of ethnic identity, acculturation, and familism as well as suggestions for future research are discussed.