Adenoid cystic carcinoma (ACC) of the sublingual gland is an extremely rare neoplasm. The clinicopathological characteristics of ACC are slow-growing swelling with or without ulceration, perineural spread, local recurrence, and distant metastasis. This report describes a 58-year-old male who had a slowly growing swelling without ulceration on the right side of the mouth floor that had been present for 1 month. In a radiological examination, the mass showed multilocular cystic features and no bony or tongue muscle invasion. No enlarged cervical lymph nodes were detected. Excisional biopsy and histological analysis showed that the lesion was ACC. In addition to reporting a rare case of ACC, this report also discusses the differential diagnosis and treatment of ACC with a review of the relevant literature.