Background <p>Dermoid cysts with plunging presentation in the Oral and Maxillofacial region are uncommon developmental lesions. They often represent a very small proportion of oral pathologies and an even smaller subset of dermoid cysts occurring elsewhere in the body. Their clinical resemblance to other cystic swellings occurring in the floor of the mouth and submental region often makes diagnosis challenging, necessitating radiological and histopathological correlation.</p> Case Presentation <p>A 39 years old woman reported with a painless swelling in the submental region. Initial clinical assessment and radiological findings suggested a diagnosis of plunging ranula and was managed by surgical excision. However, histopathological examination of the excised specimen revealed features consistent with a plunging dermoid cyst, thereby revising the final diagnosis.</p> Conclusion <p>This case highlights the importance of considering a plunging dermoid cyst in the differential diagnosis of submental swellings. Correlation between clinical findings, imaging characteristics, and histopathological evaluation is crucial for accurate diagnosis and appropriate treatment planning. Increased awareness of this rare entity may help reduce diagnostic errors in similar presentations. A brief review of the relevant literature is also presented.</p>