Objective: To examine the outcomes of patients with a positive surgical margin by gross and/or frozen examination during partial nephrectomy, in whom a re-resection of the margin or a completion nephrectomy was performed. Methods: Patients with renal cancer who underwent partial nephrectomy were considered. If the patient had a positive margin and underwent completion nephrectomy or re-excision of the margin, they were included. Patients with planned enucleation were excluded from the study. Clinical and pathologic information were reviewed to examine for residual cancer in the additionally resected tissue. Results: In the final cohort, 29 patients with a positive margin and subsequent complete parenchymal re-resection or completion nephrectomy were identified. Eight patients underwent nephrectomy, after which no residual cancer was found in the renal remnant. Twenty-one patients underwent total re-resection of the margin, of which two were found to have carcinoma. Renal functional outcomes revealed a decrease in estimated glomerular filtration rate of 25 mL/min/1.73 m2 in patients who underwent radical nephrectomy, and 4 mL/min/1.73 m2 in patients who underwent re-resection of the margin with preservation of the renal unit. Conclusions: A positive surgical margin does not necessarily mean that cancer remains in the renal remnant in most cases. Therefore, radical nephrectomy or re-resection of the margin is overtreatment in many cases, but a small percentage of patients will harbor residual malignancy. Clinical correlation is recommended before reexcision or completion nephrectomy after a positive surgical margin, with careful consideration of the impact on subsequent renal function weighed against the possibility of residual disease.