Purpose: The purpose of this study was to identify symptom clusters in patients with breast cancer and to investigate the associations among them with functional status and quality of life (QOL). Methods: A convenient sample of 303 patients was recruited from an oncology-specialized hospital. Results: Two distinct clusters were identified: A gastrointestinal- fatigue cluster and a pain cluster. Each cluster significantly influenced functional status and QOL. Based on these two clusters, we identified subgroups of symptom clusters using K-means cluster analysis. Three relatively distinct patient subgroups were identified in each cluster: mild, moderate, and severe group. Disease-related factors (i.e., stage, metastasis, type of surgery, current chemotherapy, and anti-hormone therapy) were associated with these subgroups of symptom clusters. There were significant differences in functional status and QOL among the three subgroups. The subgroup of patients who reported high levels of symptom clusters reported poorer functional status and QOL. Conclusion: Clinicians can anticipate that breast cancer patients with advanced stage, metastasis, and who receive mastectomy, and chemotherapy will have more intense gastrointestinal-fatigue or pain symptoms. In order to enhance functional status and QOL for patients with breast cancer, collective management for symptoms in a cluster may be beneficial.