We examined profiles of sibling relationship qualities in 246 Mexican-origin families living in the United States using latent profile analyses. Three profiles were identified: Positive, Negative, and Affect-Intense. Links between profiles and youths’ familism values and adjustment were assessed using longitudinal data. Siblings in the Positive profile reported the highest familism values, followed by siblings in the Affect-Intense profile and, finally, siblings in the Negative profile. Older siblings in the Positive and Affect-Intense profiles reported fewer depressive symptoms than siblings in the Negative profile. Further, in the Positive and Negative profiles, older siblings reported less involvement in risky behaviors than younger siblings. In the Negative profile, younger siblings reported greater sexual risk behaviors in late adolescence than older siblings; siblings in opposite-sex dyads, as compared to same-sex dyads, engaged in riskier sexual behaviors. Our findings highlight sibling relationship quality as promotive and risky, depending on sibling characteristics and adjustment outcomes.