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.