Ovarian cystic teratomas are one of the commonest benign, pelvic tumors. However, its infiltration into the urinary bladder is not frequently reported. We present a rare case of beenign dermoid cystic teratoma of ovary infiltrating urinary bladder. This was observed in a 40-year-old multiparous women at department of Gynaecology. Ultrasonography of her abdomen showed an ill-defined heterogenous lesion (3.6x2.8 cm) in the left adnexa of the uterus with calcific and cystic areas within; adherent to the base of the bladder suggestive of inflammatory or neoplastic tubo ovarian pathology. The cystoscopic observations confirmed the infiltration of posterior wall of the urinary bladder by the tumour with e/o of tufts of hair and calcification. CT scan of abdomen showed a heterogenous lesion in the left adnexa of uterus with calcification, haemorrhage and cystic areas within, with poorly defined fat plane with adjacent urinary bladder. In addition, multiple cystic lesions in the right adnexa of uterus with linear calcification in the urinary bladder with diffuse thickening of the bladder wall was also observed. Histopathology reports confirmed the tumour to be a benign cystic teratoma of left ovary with adherence and rupture into the bladder with no evidence of malignancy. During surgery, a 4x4 cm solid tumour was found towards the lateral end of the ovary infiltrating the bladder above and posteriorly. The bladder was opened up and the part of the bladder wall 6x6 cm size with tuft of hair and yellowish white cheesy material, which included the base and periphery of tumour was excised and bladder wall repaired in layers after placing a Malecot's catheter.