Salivary gland diseases are diverse, including neoplastic, cystic and inflammatory diseases, and are often difficult to diagnose. Ranula is a mucous retention cyst often encountered clinically. Sialolithiasis is usually caused by the submandibular gland; reports identifying the sublingual gland as the cause are low at 0 to 6.4%. To date, there has only been one case report of a combination of ranula and sialolith. We report a case of sublingual-plunging ranula containing sialoliths with ossification. The patient was a 17-year-old female referred to our hospital with painful swelling in the right submandibular region. The clinical findings included mild swelling of the right submandibular region, and a sialolith-like hard substance palpable in the right floor of the mouth. Contrast-enhanced computed tomography and contrast-enhanced magnetic resonance imaging showed a cyst-like lesion from the right sublingual space to the submandibular space, and three sialolith-like calcifications were found in the cyst. The clinical diagnosis was right-sided sublingual-plunging ranula containing multiple sialoliths, and the patient underwent a sublingual gland excision, ranula excision and salivarylithotomy under general anesthesia. The resected specimen showed three stones encapsulated in the cyst contiguous to the sublingual gland.