Engagement in risk behavior has implications for individuals' academic achievement, health, and well-being, yet there is a paucity of developmental research on the role of culturally relevant strengths in individual and family differences in risk behavior involvement among ethnic minority youth. In this study, we used a longitudinal cohort-sequential design to chart intraindividual trajectories of risk behavior and test variation by gender and familism values in 492 youth from 12 to 22 years of age. Participants were older and younger siblings from 246 Mexican-origin families who reported on their risk behaviors in interviews spaced over 8 years. Multilevel cohort-sequential growth models revealed that youth reported an increase in risk behavior from 12 to 18 years of age, and then a decline to age 22. Male youth reported greater overall levels and a steeper increase in risk behavior from ages 12 to 18, compared to female youth. For familism values, on occasions when youth reported higher levels, they also reported lower levels of risk behavior (i.e., within-person effect). For sibling dyads characterized by higher average levels of familism values, youth reported lower average levels of risk behavior (i.e., between-family effect). Findings provide unique insights into risk behavior from adolescence to young adulthood among Mexican-origin youth.