Dermoid cysts or mature cystic teratomas are mostly benign, and account for about 30–45% of all ovarian neoplasms [1]. Malignant transformation is seen in about 0.17–1.4% [2]. Squamous cell carcinoma is the most common type of malignant change. Due to lack of typical clinical features and non specific tumour markers in addition to no classical radiological picture they are difficult to diagnose pre operatively. Stage III or IV disease have a poor prognosis and have a poor five year survival. Here, we are presenting a case of squamous cell carcinoma arising in a dermoid cyst of the ovary in a 40 year old woman with previously operated dermoid , who presented with a large tubo–ovarian mass, for which she was operated and histopathology confirmed squamous cell carcinoma arising from the dermoid.