BACKGROUND: Colloid cysts (CCs) are rare cystic lesions derived from the endoderm of the central nervous system. Although they appear most commonly in the anterior roof of the third ventricle, there are only a few reports of CCs located in the suprasellar region. Although CCs are considered to be slow-growing benign tumors, their developmental process remains unclear. CASE DESCRIPTION: A 6-year-old boy was referred to our hospital for a mild head injury. Head computed tomography scan revealed a round, hyperdense suprasellar lesion, while magnetic resonance (MR) imaging depicted the mass as an isointense lesion with multiple highly hypointense spots on T2-weighted imaging. Although this lesion had been managed conservatively with annual MR imaging follow up, its size gradually increased, resulting in an increase in diameter by a factor of 1.5 over an 11-year period. The doubling time of this tumor was estimated to be approximately a 7 years. Despite its asymptomatic nature, the cystic lesion was totally resected when the patient was 17 years of age using an endoscopic endonasal approach to make a definitive histological diagnosis and prevent the occurrence of neurological symptoms. The postoperative course was uneventful, and the histological diagnosis of the surgical specimen was consistent with CC. CONCLUSIONS: This case suggests that CC may be one of several possible diagnoses in patients who present with suprasellar cystic lesions. Even if CCs in the suprasellar region remain asymptomatic, radiological follow-up is required due to possible progressive enlargement of the cyst.