The benefit of completion lymph node dissection (CLND) in melanoma patients with a positive sentinel lymph node (SLN) remains unknown. We identified patients with a positive SLN from 1994 to 2012. Patient and tumor characteristics, reasons for not undergoing CLND, patterns of recurrence, and melanoma-specific survival data were analyzed. Of 4,310 patients undergoing SLN biopsy (SLNB), 495 (11 %) had a positive SLN—167 (34 %) patients underwent nodal observation and 328 (66 %) had immediate CLND. Patients in the no-CLND group were older (66 vs. 56 years; p < 0.001) and more likely to have lower extremity lesions (57 vs. 42 %; p = 0.006). There were no differences in tumor thickness, Clark level of invasion, ulceration, or SLN tumor burden. Median follow-up was 23 and 80 months for the no-CLND and CLND groups, respectively, and median time to recurrence was similar at 9 and 12 months, respectively (p = 0.48). There was no difference in local and in transit recurrence rates between groups (16 %, no CLND, and 18 %, CLND; p = 0.48). Nodal disease as a site of first recurrence occurred in 15 % of patients in the no-CLND group and 6 % of CLND patients (p = 0.002). In contrast, systemic recurrences occurred in 8 % of no-CLND patients compared with 27 % of CLND patients (p < 0.001). While median recurrence-free survival was higher after CLND (34.5 vs. 20.9 months; p = 0.02), melanoma-specific survival was similar (not reached, no CLND vs. 110 months, CLND; p = 0.09). Immediate CLND after a positive SLNB is associated with fewer initial nodal basin recurrences but similar melanoma-specific survival. These results support ongoing equipoise in the Multicenter Selective Lymphadenectomy Trial II (MSLT-II).