Background: Fear of recurrence is a common yet underappreciated burden patients experience during and after cancer treatment. Medical misinformation about factors that influence risk of cancer progression/recurrence is also common. Little is known about the spread of medical misinformation and how it affects fear of cancer recurrence. Methods: From 7/2023 to 8/2023 patients completed an anonymous online survey administered by Breastcancer.org. Surveys were available in English and Spanish with eligibility: US resident, age ≥18 years, and breast cancer diagnosis within 10 years. Surveys assessed patient awareness of various factors purported to increase or decrease risk of cancer progression/recurrence and fear of recurrence (via validated FCRI-SF, scored 0-36, higher scores indicate greater fear, score ≥22 indicate clinical relevance). Multivariate analysis (MVA) assessed awareness of misinformation after controlling for age, race and ethnicity, marital status, and level of education. Chi-square assessed association between misinformation exposure and fear of recurrence. Results: Overall, 997 completed the survey. Median age was 62 (IQR 53-69), 86% were White, 5% Black, 4% Hispanic, and 3% Asian. 76% were married and 77% had completed a college or advanced degree. 52% were undergoing active cancer treatment at the time of assessment. Most (65%) reported hearing misinformation regarding factors that may INCREASE risk of cancer progression/recurrence. Specifically, patients heard that sugar (61%), deodorant (22%), vaccines (8%), cell phones (8%), and bra type (8%) could increase risk. Half (54%) reported hearing misinformation regarding factors that may DECREASE risk of cancer progression/recurrence. Specifically, patients heard that eating organic food (41%), oral vitamins/supplements (29%), alkaline diet/alkalized water (12%), vitamin infusions (7%), cleanses (5%), essential oils (5%), and oxygen therapy (4%) could decrease risk. Overall, 76% had reported at least one incorrect factor influencing risk of cancer progression/recurrence. On MVA, younger age (OR 0.99/year of age, 95%CI 0.97-1.00, p=0.044) and Hispanic ethnicity (OR 2.98, 95%CI 1.02-8.25, p=0.047) were associated with hearing misinformation. Fear of recurrence score was available for 695 (70%) patients. Median score was 19 (IQR 13-24), 38% had a clinically significant level of fear (≥22). Awareness of medical misinformation was not associated with clinically significant fear (38% vs. 35%, χ² 0.53, p=0.469). Conclusions: In a large cohort of patients with breast cancer, medical misinformation about risk of progression/recurrence was common. Fear of recurrence was high in over a third of surveyed patients, but was not associated with awareness of false information. Further understanding of how patients perceive and process medical misinformation is essential, especially in populations at highest risk for misinformation spread.