This study aimed to examine the prevalence of psychological distress and the corresponding risk factors among patients with breast cancer affected by the outbreak of coronavirus disease 2019 (COVID-19). This cross-sectional, survey-based, region-stratified study was conducted from March 14 to March 21, 2020. An online survey was used to collect the basic characteristics of patients with breast cancer. The degree of depression, anxiety, and insomnia symptoms were assessed using the Patient Health Questionnaire (PHQ-9), the Generalized Anxiety Disorder (GAD-7), and the Insomnia Severity Index (ISI) questionnaires, respectively. Multivariate logistic analysis was performed to identify factors associated with psychological distress outcomes. Among the 834 patients with breast cancer included in the study, the prevalence of depression, anxiety, and insomnia was 21.6%, 15.5%, and 14.7%, respectively. No statistically significant difference in the prevalence of these symptoms was observed between patients in Wuhan and those outside Wuhan. Multivariate logistic regression analyses revealed that comorbidity, living alone, deterioration of breast cancer, and affected treatment plan were risk factors for psychological distress including depression, anxiety, and insomnia. When stratified by location, living alone was associated with depression and insomnia only among patients in Wuhan, but not those outside Wuhan. This study shows an elevated prevalence of depression, anxiety, and insomnia among patients with breast cancer during part of the COVID-19 pandemic. Patients with comorbidity, living alone, deterioration of breast cancer, and whose treatment plan was affected should be paid more attention to prevent mental disorders.