Background: The COVID-19 pandemic has caused unprecedented stressors on the mental health of patients with cancer as well as with cancer survivors. Little is known regarding anxiety among breast cancer survivors during and following the pandemic. Methods: We performed a cross-sectional study evaluating the mental health impacts of the COVID-19 pandemic on a cohort of breast cancer survivors (n = 1333). Between January and March 2022, participants enrolled in the Rays of Hope Breast Cancer Research Registry were invited to complete an online study questionnaire. We analyzed the data collected from a series of questions regarding outcomes and perspectives representing three distinct time periods: before (prior to March 2020), during (March 2020-June 2021) and after the COVID-19 pandemic (January-March 2022), based on the dates of the Massachusetts State of Emergency declaration. The COVID-19 Anxiety Scale (CAS) was used to measure anxiety specific to COVID-19. Generalized anxiety symptoms were measured using the Generalized Anxiety Disorder 7-item (GAD-7) scale. Multinomial logistic regression was used to identify factors related to increased or decreased anxiety symptoms. Results: A total of 272 independent participants (21.5%) completed the survey. Of these, 230 respondents with a confirmed history of breast cancer were included in the final analysis. While 26.2% met GAD-7 criteria for moderate to severe anxiety after the pandemic, only 13% self-reported a prior diagnosis of any mental health condition. Approximately 17% reported experiencing more anxiety symptoms after the pandemic compared to before. A history of smoking was associated with a higher likelihood of experiencing increased symptoms of generalized anxiety (OR = 1.97, 95% CI 0.93-4.14); whereas exercise frequency of at least three times per week was associated with experiencing a decrease in anxiety symptoms over this period (OR = 7.00, 95% CI 1.39-35.14). The CAS and reporting that the pandemic had a negative impact on cancer care were associated with a higher likelihood of increased generalized anxiety after the pandemic (OR = 2.21, 95% CI 1.19-4.09; OR = 3.05, 95% CI 1.06-8.83, respectively). Conclusions: Increased symptoms of anxiety were prevalent among breast cancer survivors during the pandemic and, in some, have not returned to pre-pandemic levels. Less than half of participants with symptoms meeting criteria for moderate to severe anxiety reported having a formal medical diagnosis, suggesting that clinically significant anxiety may be underrecognized in breast cancer survivors following the pandemic.