In order to determine the extent and time course of upper limb impairment and dysfunction in women being treated for breast cancer (BC), and followed prospectively, a novel physical therapy surveillance model post-treatment was used. Subjects included adult women with newly diagnosed, untreated, unilateral, Stage I to III BC, and normal physiological and biomechanical shoulder function. Subjects were excluded if they had a previous history of BC, or prior injury or surgery of the affected upper limb. Measurements included body weight, shoulder ranges of motion (ROM), manual muscle tests, pain levels, upper limb volume, and an upper limb disability questionnaire (ULDQ). Measurements were taken at baseline (pre-surgery), and 1, 3-6, and 12 months post-surgery. All subjects received pre-operative education and exercise instruction and specific physical therapy (PT) protocol after surgery including ROM and strengthening exercises. All measures of function were significantly reduced 1 month post-surgery, but most recovered to baseline levels by 1-year post-surgery. Some subjects developed signs of lymphedema 3-12 months post-surgery, but this did not compromise function. Shoulder abduction, flexion, and external rotation, but not internal rotation ROM, were associated with the ULDQ. Most women in this cohort undergoing surgery for BC who receive PT intervention may expect a return to baseline ROM and strength by 3 months. Those who do not reach baseline, often continue to improve and reach their pre-operative levels by 1-year post-surgery. Lymphedema develops independently of shoulder function 3-12 months post-surgery, necessitating continued monitoring. A prospective physical therapy model of surveillance allows for detection of early and later onset of impairment following surgery for BC in this specific cohort of patients.