OBJECTIVE: To investigate the type of upper limb dysfunctions and to determine major dysfunctions influencing on the quality of life (QoL) in the early phase after mastectomy. METHOD: Among the female patients with mastectomy after diagnosed as breast cancer followed by chemotherapy and/or radiation therapy, 38 patients who had shoulder pain or arm edema were selected. Visual analog scale (VAS) for pain at rest and during activity, range of motion of shoulder and arm circumference were measured. Disabilities of Arm, Shoulder and Hand (DASH) and Short form-36 v2 questionnaire were used to assess the functional disability and health-related QoL. RESULTS: Lymphedema (31.6%), limitation of motion (31.6%) and shoulder pain (26.3%) were major dysfunctions. Patients who had limited motion showed more severe dysfunctions. The cases with shoulder pain showed low level of QoL in mental component. VAS during activity and activity of daily living (ADL) domain of DASH were major impact factors on QoL related to physical functioning. In mental component, social domain of DASH was the most influencing factor on QoL. CONCLUSION: Pain during activity, limited ADL and social activity were major problems lowering QoL in patients with breast cancer. The proper managements for these problems is needed.