This study examines age of first cigarette, alcohol, and marijuana use among self-identified biracial youth, using data from the National Longitudinal Study of Adolescent Health (Add Health). We found an intermediate biracial phenomenon in which some biracial youth initiate substance use at ages that fall between the initiation ages of their 2 corresponding monoracial groups. When controlling for the covariates, our findings show White-Asian biracial youth begin smoking marijuana and drinking alcohol at earlier ages than Whites and engaging in all forms of substance use at earlier ages than Asian youth. Results indicate White-American Indian youth start smoking cigarettes at earlier ages than all biracial and monoracial groups. Our findings underscore the need for future research to examine substance-use initiation and progression among biracial/ethnic youth.