Arachnoid cysts (ACs) are a rare condition of mass effect injury and are usually found in the Sylvian fissure. However, rarely, they can appear in the sellar area, causing symptoms of compression. Due to the mass effect, the sellar arachnoid cyst (SAC) may cause headaches, visual disturbances, hypopituitarism, precocious puberty, and the “bobble-head doll” syndrome. We present the case of JNS, 61 years old, male. The patient presented with hypotestosteronism, hypothyroidism, hypocortisolism and bitemporal hemianopsia. The magnetic resonance imaging scans revealed a mass above the pituitary gland, compatible with a SAC. A surgical excision was performed with removal of the capsule and fenestration within the subarachnoid spaces for emptying the cyst. After the procedure, the patient presented great clinical improvement. The rarity of the case calls attention to the fact that SACs should be thought of as a differential diagnosis in cases of hypopituitarism.