With improved survivorship, the prevalence of breast cancer-related lymphedema (BCRL) continues to increase, leading to impairment of a patients' quality of life. While traditional diagnostic methods are limited by an inability to detect BCRL until clinically apparent, bioimpedance spectroscopy (BIS) has been shown to detect subclinical BCRL. The purpose of this study is to evaluate the role of BIS in the early detection of BCRL, as well as assessment of response to BCRL treatment. A retrospective review of 1,133 patients treated between November 2008 and July 2013 at two surgical practices was performed. Eligible patients (n = 326) underwent preoperative and postoperative L-Dex measurements. Patients were identified as having subclinical lymphedema if they were asymptomatic and the L-Dex score increased >10 U above baseline and were monitored following treatment. Patients were stratified by lymph node dissection technique [sentinel lymph node biopsy (SLNB) vs. axillary lymph node dissection (ALND)] and receipt of BCRL treatment. The average age of the cohort was 56.2 years old, and mean follow-up was 21.7 months. Of the 326 patients, 210 underwent SLNB and 116 underwent ALND. BCRL was identified by L-Dex in 40 patients (12.3%). The cumulative incidence rate of subclinical lymphedema was 4.3% for SLNB (n = 9) and 26.7% for ALND (n = 31). Of those diagnosed with BCRL, 50% resolved following treatment, 27.5% underwent treatment without resolution, and 22.5% had resolution without treatment. The prevalence of persistent, clinical BCRL was 0.5% for SLNB and 8.6% for ALND. This study demonstrates both the feasibility and clinical utility of implementing L-Dex measurements in routine breast cancer care. L-Dex identified patients with possible subclinical BCRL and allowed for assessment of response to therapy.