Mucinous cystadenocarcinoma of minor salivary glands is an extremely rare entity that has only recently been described, with a few published cases in the English literature. A 42-year-old woman with a history of a surgically excised mucinous cystadenoma of the oral tongue, presented with a painful swelling in the oral tongue slowly growing for 1 month. On clinical examination, there was a firm, relatively well-circumscribed mass in the left posterior border of the mobile tongue. Subsequent MRI scan revealed a heterogeneous lesion composed of multiple cysts separated by contrast enhancing septa, in the posterior two-thirds of the left tongue. Imaging findings were similar to those of the previously resected mass, suggesting local relapse of the primary lesion. A complete surgical excision was performed and the histopathological examination revealed typical features of a low-grade mucinous cystadenocarcinoma of minor salivary glands.