Growth Hormone (GH) deficiency incidence in infants is reported to be 1 in 3800 live births, and although adequate data are missing, it is thought to be rising among older children due to increased survival after childhood malignancies. The main effect of GH deficiency in childhood is growth failure and it is treated with exogenous growth hormone replacement. Treatment with GH in childhood is generally without serious complications and the most common side effects reported are listed as headache, joint/muscle pains, şuid retention, mild hypertension, visual problems, nausea/ vomiting, paresthesia, antibody formation, reactions at injection site and rarely, being intracranial hypertension. Here, we report a case of mood disorder with mixed features in a pre-pubertal child, which was possibly related with exogenous GH replacement. The patient was an 11-year-old male, who was brought to our department with complaints of “insomnia, talkativeness, increased energy and spending”. Upon questioning, it was learnt that the complaints were present for the last 3 months. He was inattentive, hyperactive, euphoric and it was reported that “he felt he could do anything”. His grades suffered and within the last month he verbalized suicidal ideations to his teachers. Mental status examination revealed auditory hallucinations, grandiose delusions alternating with depressive ruminations and limited insight. The medical and psychiatric history was unremarkable except growth failure, which led to a referral to the pediatrics department 4 months ago. The patient was diagnosed with GH deficiency and GH injections were commenced 3 months ago. Apart from mild memory problems and irritability, no depressive episode was reported prior to treatment with GH. Family history was negative for psychopathology. A neurological examination ruled out papillary edema and no signs or symptoms of intracranial hypertension were reported. Psychometric evaluation with the Childhood Mania Scale as completed by the parents revealed a score of 35 (chief complaints: auditory hallucinations, paranoid ideations, impulsivity, grandiosity, pressured speech, insomnia, increased energy, euphoria and irritability). The baseline evaluation with Young Mania Rating Scale yielded a score of 38. Childhood Depression Inventory and other measures could not be completed due to excessive hyperactivity. The patient was moderately impaired due to his symptoms as rated with Children’s Global Assessment Scale (CGAS) revealing a score of 45. Consequently, the patient was diagnosed to have Mood Disorder with Mixed Features due to Exogenous GH, according to DSM-IV criteria and treatment was started with risperidone 0.5 mg/ day, later titrated to 1 mg/day. A follow-up visit after 2 weeks revealed a YMRS score of 24 and a CGAS score of 55 (Variable functioning). Because of persisting grandiose delusions and depressive ruminations, valproate 200 mg/ day was added on and a follow- up visit is planned. Here we report a case of mood disorder with mixed features in a pre-pubertal child. An evaluation with the Naranjo Algorithm yielded a score of 4 (Possible Adverse Drug Reaction, 3) and the patient responded partially to a trial of antipsychotics and mood-stabilizers. As a result, it can be said that exogenous GH in children may lead to secondary mood disorders. Our results should be confirmed with future studies.