Although the construct of impulsivity has generally been found to be associated with obesity and health behaviors in adults, research among adolescents is more limited and studies have yet to elucidate which facets of impulsivity may be most salient with regard to different eating and physical activity behaviors. Therefore, the present cross-sectional study assessed facets of impulsivity, measured by the UPPS-P questionnaire, in relation to health behaviors among adolescents. A sample of 2797 high school students from Los Angeles, California completed self-report measures during the ninth grade. The UPPS-P subscales (i.e., (lack of) premeditation, sensation seeking, (lack of) perseverance, negative urgency, positive urgency) were examined as predictors of unhealthy diet quality (i.e., frequency of consumption of high-fat foods and sweet food and drinks, measured by the National Cancer Institute (NCI) Quick Food Scan) and frequency of vigorous physical activity (measured by the Youth Risk Behavior Surveillance System). Greater sensation seeking, positive urgency, and negative urgency was associated with greater unhealthy diet quality (ps < 0.001). Greater negative urgency and lack of perseverance was associated with less frequent vigorous physical activity, whereas greater sensation seeking, lack of premeditation, and positive urgency was associated with more frequent vigorous physical activity (ps < 0.05). While negative urgency (i.e., impulsivity in the context of negative emotions) was consistently associated with poor health behaviors, other facets of impulsivity may potentiate vigorous physical activity in youth. Together these findings underscore the importance of considering the multidimensional nature of impulsivity in relation to adolescents’ health behaviors and highlight areas for future longitudinal research.