Completion thyroidectomy is recommended in patients who have been diagnosed with differentiated thyroid cancer on histopathological evaluation, if their first operation was a conservative approach. The critical issue is when to do the second operation.The medical records of 66 patients who underwent completion thyroidectomy for the treatment of differentiated thyroid cancer in our clinic between 2006-2013 were retrospectively analyzed. All data were compared after patients were divided into two groups according to the interval between the first surgery and completion thyroidectomy.Fifty-two patients (78.8%) were women and 14 patients (21.2%) were male. Completion thyroidectomy was performed 10-90 days after the initial surgery (group 1) in 26 patients, whereas it was performed later than 90 days in 40 patients (group 2). Temporary hypoparathyroidism occurred in two patients (7.7%) in group 1, and in 3 patients (7.5%) in group 2. Transient recurrent laryngeal nerve palsy was observed in 1 patient (3.9%) in group 1, and in 1 patient (2.5%) in group 2. There were no permanent morbidities in both groups. Residual tumor rate after completion thyroidectomy was 45.5%. There was no statistically significant difference between the two groups in terms of complications after completion thyroidectomy.Although in some studies it is recommended that completion thyroidectomy should be performed either before scar tissue development or after clinical remission of scar tissue, edema and inflammation, we believe that timing of surgery has no effect on morbidity.