Persistent/recurrent disease in the neck is frequent in patients with differentiated thyroid cancer (DTC). Assess efficacy, safety, and prognostic factors of first neck reoperation in DTC. Retrospective study of consecutive patients undergoing neck reoperation for recurrent/persistent DTC in a referral cancer center. Response after reoperation was defined according to the 2015 American Thyroid Association guidelines. One hundred sixty-one DTC patients were enrolled (64% females, median age 35 years, 96% papillary DTC). Initial stage was pT3 in 43% and pT4 in 10%, pN1 in 74%. Aggressive histology was present in 25% of the patients, in both primary and persistent/recurrent tumor. Four patients had no malignancy in the reoperative specimen, and 1 patient died due to postoperative hematoma and was excluded from further analysis. Following reoperation, 15 patients (10%) had persistent structural disease, 16 (10%) had biochemical incomplete response, 26 (17%) had indeterminate response, and 99 (63%) had complete response (CR), among whom 24 relapsed later. After a median follow-up of 5 years, only 83 patients (53%) had CR without the need for further treatments. The rate of permanent complications was: hypoparathyroidism 2%, laryngeal nerve palsy 0.6%, other 6%. Age ≥45 years, aggressive histology, and lymph node ratio ≥0.6 at initial surgery were independent risk factors for incomplete response after reoperation. Male sex, aggressive histology, and ≥10 metastases at reoperation were independent risk factors of secondary relapse following CR achieved with reoperation. A careful risk-benefit analysis should guide surgical decision, particularly in patients with risk factors for incomplete response.