Background: Postoperative hypocalcemia is a frequent complication after thyroid surgery. Hypoparathyroidism may develop as transient (TtHP), with normalization within six months from surgery, or permanent (PtHP) if the patient requires replacement therapy. The present study analyzes rates and factors associated with the development of TtHP or PtHP following thyroid surgery in a pediatric population. Procedure: A retrospective multicenter study analyzing 363 patients was carried out. We recorded gender, age, tumor size, type of surgery, lymph node dissection, histology. Calcium levels were acquired daily for 72 hours after discharge. Subsequent sample collection was customized on the patient’s hypocalcemia severity. Results: We analyzed 363 patients aged ≤18 years (mean age 14.2 years) who underwent thyroid surgery clustered into age groups (≤15 or >15). Patients mean follow-up was 5.8 years (1-11yrs). At histology 310 (85%) were papillary carcinoma, 32 (9%) were follicular carcinoma, 6 (2%) presented diffuse sclerosing variant of papillary thyroid carcinoma whilst 15 (4%) had familial medullary carcinoma. TtHP developed in 36 (9,9%), PtHP in 20 (5.5%) cases. TtHP was more frequent in younger patients (p=0,009). Both PtHP and TtHP were increased in case of larger tumors (≥2 cm) (p=0,001). All TtHP and PtHP were in TT group. PtHP rate was increased if lymph node dissection was carried out (p<0.001). Conclusions: The risk of hypoparathyroidism is related to younger age, tumor size, TT and lymph node dissection therefore surgeons should tailor surgery as much as possible to avert such complication.