Objective: The significance of positive margin in favorable-stage well-differentiated thyroid cancer is controversial. We report outcomes of positive-margin patients with a matched-pair comparison to a negative-margin group. Materials and Methods: A total of 25 patients with classic-histology papillary or follicular carcinoma, total thyroidectomy +/− node dissection, stage T1-3N0-1bM0, positive surgical margin at primary site, adjuvant radioactive iodine (I-131), and age older than 18 years were treated between 2003 and 2013. Endpoints were clinical and biochemical (thyroglobulin-only) recurrence-free survival. Matched-pair analysis involved a 1:1 match with negative-margin cases matched for overall stage and I-131 dose. Results: Recurrence-free survival in positive-margin patients was 71% at 10 years. No patient was successfully salvaged with additional treatment. Only 1 patient died of thyroid cancer. Recurrence-free survival at 10 years was worse with a positive (71%) versus negative (90%) margin (P=0.140). Conclusions: Cure with a microscopically positive margin was suboptimal (71%) despite patients having classic-histology papillary and follicular carcinoma, favorable stage, and moderate-dose I-131 therapy.