Accurately measuring children’s emotion reactivity and regulation is important both for advancing theoretical understanding of child development and for identifying and monitoring children who have difficulties with emotional competence. Children have a uniquely important perspective on their own internal experiences of emotion reactivity and regulation that may differ from observers. However, there are few child-report measures of emotion reactivity and regulation. The goal of the present study was to develop and assess the psychometric properties of a child self-report measure of emotion reactivity and regulation (Youth Emotions Scale; YES) for elementary school-aged children. Examination of psychometric properties in a sample of 277 children (5 to 12 years old) oversampled for risk for emotional difficulties indicated good validity and reliability. Factor analyses indicated two theory-consistent factors (Reactivity and Emotion Regulation Strategies), both of which showed convergent and concurrent validity based on parent and child self-report of related constructs. This scale has both clinical and research utility, as having a brief measure of both emotion reactivity and regulation can aid clinicians and researchers in attaining relevant information without overtaxing children with multiple long measures. Future research should explore psychometric properties of the YES across different samples with different characteristics; if its validity continues to be supported, clinicians and researchers can utilize the YES to capture children’s internal experiences of emotion reactivity and regulation in treatment and research.