OBJECTIVE Risk factors for the rare and unique entity of paediatric thyroid cancer are becoming more clearly defined. This study investigated the association of thyroid-stimulating hormone (TSH) with the diagnosis of differentiated thyroid carcinoma in the paediatric population. No previous studies have correlated the paediatric thyroid cancer risk with TSH levels. DESIGN Retrospective case-controlled study. PATIENTS A total of 116 paediatric patients with an indication for thyroidectomy referred to Seattle Children's Hospital, a major paediatric tertiary medical centre, between January 1997 and January 2011 were assessed. Excluding confounders that would directly affect TSH values, 78 patients (29 patients with and 49 patients without thyroid cancer) between the ages of 3 and 20 years were evaluated. MEASUREMENTS Preoperative TSH values correlated with pathology review of en bloc resected thyroid tissue specimens. RESULTS The diagnosis of paediatric thyroid carcinoma was significantly associated with elevated TSH levels. The average TSH level (2·32 ± 0·51 mIU/l) was significantly greater than the TSH level (1·08 ± 0·14 mIU/l) noted in patients without malignancy (P = 0·03). A rightward skew of TSH was associated with paediatric patients harbouring paediatric thyroid carcinoma, with a TSH level ≥2·50 mIU/l correlating with a significantly increased odds ratio of thyroid cancer (OR 8·05, 95% CI 1·41-81·39, P = 0·0073) relative to a normal TSH range of 0·40-2·49 mIU/l. CONCLUSIONS Paediatric thyroid carcinoma is associated with TSH level ≥ 2·50 mIU/l, which may be useful to identify a higher risk of malignancy in a paediatric patient with a thyroid nodule.