Malignant transformation in a mature cystic teratoma of the ovary is rare, occurring in only 1-2% of cases, with squamous cell carcinoma consisting of about 75% of malignant transformations. Various genomic alterations take part in this pathogenesis but due to its rare incidence, not many cases have been reported in respect to this transformation. Hence, we describe a rare case of 45-year-old female with a 7.5 cm ovarian mature teratoma with an incidental finding of squamous cell carcinoma. With this case report, we also wish to create an awareness of this entity among pathologists and physicians while dealing with dermoid cysts of large sizes in older patients.