Breast cancer surgery is associated with upper-body morbidities that may last several years postsurgery. Research has not determined if the type of surgery leads to differential effects on shoulder function, activity levels, and QoL during the early rehabilitation period. The main objective of this study is to examine changes in shoulder function, health, and fitness outcomes from the day before to surgery to 6 months postsurgery.We recruited breast cancer patients (N = 70) scheduled to receive breast cancer surgery at Severance Hospital in Seoul to participate in this prospective study. Shoulder range of motion (ROM) and upper body strength, the disabilities of Arm, Shoulder, and Hand (quick-DASH), body composition, physical activity levels, and QoL were measured at baseline (presurgery) and then weekly for 4 weeks, and at 3 months and 6 months postsurgery.During 6 months after surgery, shoulder ROM was reduced only affected arm while shoulder strength was significantly declined in both affected and unaffected arms. Within 4 weeks postsurgery, patients who underwent total mastectomy were significantly less recovered than patients with partial mastectomy in ROM of flexion (P < .05) and abduction (P < .05). However, shoulder strength of both arms observed no interaction between surgical type and time. We observed significant changes in body composition, quick-DASH score, physical activity levels, and QoL from presurgery to 6-months postsurgery.Shoulder function, activity levels, and QoL improved significantly from surgery to 6-months postsurgery. Surgery type influenced changes in shoulder ROM.