Background: Early identification of breast cancer-related upper body issues is important to enable timely physical therapist treatment. Objective: This study evaluated the feasibility and reliability of women performing self-managed prospective surveillance for upper body issues in the early postoperative phase as part of a hospital-based physical therapy program. Design: This was a prospective, single-site, single-group feasibility and reliability study. Methods: Presurgery arm circumference measurements were completed at home and at the hospital by participants and by a physical therapist. Instruction in self-measurement was provided using a video guide. After surgery, all circumference measurements were repeated along with self-assessment and therapist assessment for shoulder flexion and abduction active range of motion. Feasibility was determined by recruitment/retention rates and participant-reported ease of performing self-measurements (1 [very difficult] to 10 [very easy]). Reliability was determined as intrarater reliability, interrater reliability, and agreement. Results: Thirty-three women who were 53.4 (SD = 11.4) years old participated, with recruitment and retention rates of 79% and 94%, respectively. Participant-reported ease of measurement was 8.2 (SD = 2.2) before surgery and 8.0 (SD = 1.9) after surgery. The intrarater reliability and interrater reliability were excellent before surgery (intraclass correlation coefficient [ICC] ≥ 0.94; 95% confidence interval = 0.87-0.97) and after surgery (ICC ≥ 0.91; 95% confidence interval = 0.76-0.96). Agreement between self-assessed and therapist-assessed active shoulder flexion (κ = 0.79) and abduction (κ = 0.71) was good. Limitations: Further testing is needed using a prospective design with a longer follow-up to determine whether self-managed prospective surveillance and timely treatment can hinder the development of chronic breast cancer-related upper body issues Conclusions: Self-measured arm circumference and shoulder range of motion are reliable, and their inclusion in a hospital-based program of prospective surveillance for upper body issues seems feasible. This approach may improve early detection and treatment