Adenoid cystic carcinoma (ACC) of the head and neck region is an uncommon epithelial tumor of the major and minor salivary glands. In the oral region, although ACC arising from the minor salivary glands is the second most commonly found tumor in the tongue base, its occurrence in the anterior part of the tongue is rare. Histopathologically, ACC is categorized into three growth patterns (tubular, cribriform, and solid types) and three histologic grades (I–III) that are based on the proportions of these patterns. According to this classification, tubular- and cribriform-type ACCs are considered to be lower grade lesions, while solid-type ACCs are considered to be higher grade lesions. A fourth histopathological type has recently been reported by some authors, namely, dedifferentiation or high-grade transformation of ACC. However, very few studies have focused on the imaging features of these ACCs. We report here the case of a 63-year-old female patient with ACC of the tongue with dedifferentiated components, together with the radiological images and pathological features of this ACC.