Familism values have been shown to have a multitude of benefits for Mexican American youth. Understanding different pathways of the adoption of familism values from adolescence and young adulthood, and predictors of these pathways, is critical. The current study assessed different classes of change in familism values across five waves from fifth grade to young adulthood, and fifth-grade predictors of these profiles, among a sample of 749 Mexican American youth. Univariate and growth mixture modeling was used to determine classes of familism change and found two classes—one class that showed small, insignificant declines across adolescence that accelerated into young adulthood and one class that showed significant declines across adolescence that stabilized and increased into young adulthood. The three-step procedure was then used to examine the following fifth-grade predictors of familism classes: family conflict, family cohesion, harsh parenting, parental acceptance, economic hardship, and perceived ethnic discrimination. Family conflict and perceived ethnic discrimination were significant predictors of familism class membership. Greater family conflict predicted a greater probability of being in the class of significant declines in familism across adolescence that stabilized and increased into young adulthood. Greater perceived ethnic discrimination predicted a greater probability of being in the class of small, insignificant decreases across adolescence that accelerated into young adulthood. Gender moderated the impact of family cohesion. For females, greater father-reported family cohesion predicted a greater probability of being in the class with significant declines during adolescence that stabilized and increased into young adulthood. For males, greater father-reported family cohesion predicted a greater probability of being in the class with slight, insignificant declines in adolescence that accelerated into young adulthood. Youth nativity moderated the impact of maternal acceptance. For youth born in the U.S., greater mother-reported acceptance predicted a greater probability of being in the class of slight, insignificant declines across adolescence that accelerated into young adulthood. For youth born in Mexico, greater mother-reported acceptance predicted a greater probability of being in the class of significant declines in familism across adolescence that stabilized and increased into young adulthood. Limitations and implications for prevention and future research are discussed.