OBJECTIVE: At the end of 1 year of the coronavirus disease (COVID-19) pandemic, we aimed to reveal the changes in breast cancer cases in the context of cause and effect based on the data of surgically treated patients in our institution. PATIENTS AND METHODS: Patients with breast cancer were divided into two groups. Group 1 consisted of patients who were operated in the year before the COVID-19 pandemic, and Group 2 consisted of patients who were operated within the first year of the pandemic. Tumor size, axillary lymph node positivity, distant organ metastasis status, neoadjuvant chemotherapy, and type of surgery performed were compared between the two groups. RESULTS: The tumor size, axillary lymph node positivity, and neoadjuvant chemotherapy were higher in Group 2 than in Group 1 (p = .005, p = .012, p = .042, respectively). In addition, the number of breast-conserving surgery + sentinel lymph node biopsy were lower, while the number of mastectomy and modified radical mastectomy were higher in Group 2 than in Group 1 (p = .034). CONCLUSION: Patients presented with larger breast tumors and increased axillary involvement during the pandemic. Moreover, distant organ metastases may increase in the future.