Objective: The present study introduces a daily, microlevel perspective on acculturation using a sample of Hispanic college students in Miami. Methods: We conducted a 12-day diary study with a sample of first-and second-generation Hispanic college students in Miami. Outcome variables were measured on Days 1 and 12, and acculturation components (practices, identities, and values) were measured on Days 2-11. Daily fluctuations in acculturation components between Days 2 and 11 were examined as predictors of well-being, internalizing symptoms, and externalizing problems on Day 12. Results: Fluctuations in comfort with speaking English negatively predicted three of the four well-being outcomes and positively predicted all of the internalizing and externalizing indicators. Fluctuations in collectivist values predicted two of the well-being outcomes and both anxiety and depressive symptoms, and fluctuations in ethnic identity predicted anxiety and depressive symptoms. Conclusion: Daily volatility in comfort with English, collectivist values, and ethnic identity appear to be most distressing.