Mast cell tumors (MCTs) are common neoplastic diseases in dogs and cats. This case report described a 2-year-old male Dwarf Djungarian Hamster (Phodopus sungorus) that presented with alopecia, pruritus, and a mass adjacent to the left ear pinna. The mass was rapidly expanding. Moreover, alopecia was observed on the right flank and ventral abdominal regions. Radiography was performed. The result revealed soft tissue opacity in the abdominal cavity. Surgical excision was performed while preserving the left ear. The histopathological result confirmed a cutaneous MCT. The medications administered consisted of antimicrobial agents, anti-inflammatory drugs, gastric protectants, and antihistamines. The hamster recovered quickly. There was no tumor recurrence. Approximately two months later, the hamster died. This is the first case report of MCTs in a hamster in Thailand. A biopsy is crucial for the diagnosis of skin masses.