BACKGROUND Patients with sentinel lymph node (SLN) metastases need delayed completion axillary lymph node dissection (ALND) if intraoperative assessment of SLN is not employed. This study was designed to compare morbidity in patients undergoing complete ALND in the first (and only) operation versus those undergoing the two-step procedure (SLN biopsy followed by delayed completion ALND). METHODS Secondary analysis of the Axillary Lymphatic Mapping Against Nodal Axillary Clearance (ALMANAC) randomized trial compared 83 patients with SLN metastases who proceeded to delayed completion ALND (two-step ALND) with 96 node-positive patients who underwent ALND as the only axillary procedure (one-step ALND). Outcome variables were assessed at baseline and at 3, 6, and 12 months after surgery. RESULTS The 83 SLN-positive patients undergoing completion ALND were younger (p = 0.038) compared with the one-step ALND group. There was no difference in lymphedema, sensory loss, intercostobrachial (ICB) nerve division rates, impairment of shoulder movement, infection rate, or time to resumption of normal day-to-day activities after surgery between the two groups. Median axillary operative time for completion ALND in the two-step group was significantly higher than one-step ALND (33 min vs. 25 min, p = 0.004). The median hospital stay for the second surgery in the two-step group was similar to one-step ALND (6 days). The total median hospital stay (first and second surgery) was significantly higher for the two-stage procedure (10 vs. 6 days, p < 0.001). CONCLUSIONS A two-stage axillary node dissection procedure in patients with SLN metastases has similar arm morbidity to one-stage ALND. The second surgery is associated with increased axillary operative time and total hospital stay.