Emotion reactivity, measured via the self-report Emotion Reactivity Scale (ERS), has shown unique associations with different forms of psychopathology and suicidal thoughts and behaviors; however, this limited body of research has been conducted among adults and older adolescents of predominantly White/European ethnic backgrounds. The present study investigated the validity of ERS scores for measuring emotion reactivity among an urban community sample of middle-school-age girls. Participants (N = 93, ages 11–15, 76% African-American, 18% Latina) completed the ERS and measures of emotion coping, internalizing problems, proactive and reactive aggression, negative life events, and lifetime suicidal ideation and substance use. As hypothesized, ERS scores were significantly associated with internalizing problems, poor emotion coping, negative life events, reactive aggression, and suicidal ideation (evidence for convergent validity), but showed little to no association with proactive aggression or lifetime substance use (evidence for discriminant validity). A series of logistic regressions were conducted to further explore the associations among internalizing problems, emotion reactivity, and suicidal ideation. With depressive symptoms included in the model, emotion reactivity was no longer uniquely predictive of lifetime suicidal ideation, nor did it serve as a moderator of other associations. In conjunction with previous research, these findings offer further support for the construct validity and research utility of the ERS as a self-report measure of emotion reactivity in adolescents.