Background: Primary care physicians (PCPs) have varying roles in a patient’s care across the cancer continuum. However, little is known about how PCP engagement and communication change over time in the transition from breast cancer treatment to longer-term survivorship. Methods: The iCanCare study is a longitudinal study of women diagnosed with breast cancer in 2014-15 identified in the Los Angeles and Georgia Surveillance, Epidemiology and End Results registries. Women were surveyed during initial treatment and again 6 years later during survivorship (2021-22) (Expected final N=1430, 60% current response rate). At both time points, respondents were asked to rate on a 5-point Likert scale, how often they talked with their PCP about their breast cancer follow up (communication), and how informed their PCP was about their breast cancer (engagement). Scores ³3 during initial treatment were considered strong. We then evaluated change in PCP engagement and communication over time from initial treatment to survivorship, with decreases reflecting worse engagement and communication. We evaluated factors associated with worse engagement and communication using multi-variable logistic regression modeling, adjusted for clinical and sociodemographic characteristics, PCP relationship, baseline communication/engagement, and COVID-19 impact. Results: In this sample of 807 women, most women reported strong PCP engagement (62.7%) and strong PCP communication (58.6%) during treatment. Over time, 40.4% reported worse PCP communication and 38.5% reported worse PCP engagement in survivorship compared to treatment(p<0.0001). Women who had comorbidities and women who changed their PCP between treatment and survivorship more commonly reported worse communication and engagement (p<0.05). Fewer women who had chemotherapy reported worse engagement and more Black and Asian women reported worse communication (p<0.05). Women who changed their PCP were more likely to report worse communication than women with the same PCP (adjusted Odds Ratio (aOR) 2.52, 95%CI: 1.52, 4.19). Women who had chemotherapy (vs. not) were less likely to report worse communication over time (aOR 0.59 CI 0.37, 0.95). Women who changed their PCP had higher odds of worse engagement over time compared to those with the same PCP (aOR 1.69, 95%CI: 1.05, 2.72). Women who had chemotherapy (vs. not) were less likely to have worse PCP engagement over time (aOR 0.59, 95%CI: 0.37, 0.92). Conclusions: In this population-based sample of breast cancer survivors, many women experienced worse communication and engagement with their PCP over time in survivorship, despite reporting high engagement and communication during initial treatment. Effective engagement and communication are key to delivery of high-quality survivorship care, thus future work focused on maintaining survivor-PCP relationships over time is needed.