Background: Latina breast cancer survivors and their caregivers face unique challenges. Acculturation is the acquisition of the cultural elements of a dominant society. Higher acculturation in Latino survivors is positively correlated with self-efficacy in patient-provider communication and improved patient-reported outcomes. There is a paucity of research on how language acculturation affects caregiver and patient outcomes. We examined associations over time between linguistic acculturation among caregivers of Latina survivors and outcomes of caregiver self-efficacy and anxiety. Methods: We partnered with four community-based organizations that serve Latino families facing cancer. We enrolled 136 Latina breast cancer survivors and their caregivers for a randomized trial comparing a dyadic coping intervention to usual care (e.g., support groups). Participants completed surveys including demographic and clinical information, the short acculturation scale for Hispanics, caregiver inventory to assess self-efficacy and PROMIS domains of anxiety at baseline and 6-months after the intervention. Results: In multivariate linear regressions models, we examined the effect of acculturation on caregiver self-efficacy and anxiety, controlling for demographics (patient and caregiver age, caregiver education, employment), patient treatment history (chemotherapy and surgery) patient and caregiver language preference (Spanish or English) and intervention arm (intervention vs. usual care). Greater caregiver self-efficacy at 6-months was associated with younger patient age (t=-2.93, p=.004), older caregiver age (t=2.63, p = .01), female caregiver gender (t=2.79, p = .006) and higher acculturation (t=2.01, p=.04), controlling for baseline self-efficacy, patient language and randomization group. Caregiver anxiety was not related to caregiver acculturation or patient language preferences. Conclusions: Caregivers’ language acculturation was significantly associated with their self-efficacy over time, suggesting that caregivers with lower acculturation experience lower confidence in their provision of care for Latina survivors. These findings are particularly salient because participants for this study were enrolled from organizations with bilingual services. Caregivers of Latina survivors without access to these community resources may face even more striking challenges. Future work can explore how caregivers’ confidence relates to survivors’ adherence to care and patient outcomes over time.