Mullerian duct anomalies result from the arrested development, abnormal formation, or incomplete fusion of mesonephric ducts. unicornuate uterus with rudimentary horn is a rare MDA of female genital tract. These patients present with dysmenorrhea, dyspareunia, and lower abdomen pain because of endometriosis. we report a rare case of a unicornuate right uterus with non–communicating left horn in a 15–year–old girl. She was presented with severe dysmenorrhea. Magnetic resonance imaging revealed a normal uterus on the right side and non–communicating rudimentary horn on left side with hematometra. She underwent laparotomy that showed a right unicornuate uterus with normal cervix and non–communicating rudimentary horn on left side containing functional endometrium with altered blood in cavity. Resection of the left rudimentary horn was done. Both ovaries were preserved. At 9 months follow up, pain subside completely and patient doing well. we are presenting a case of dysmenorrhea and hematometra in a young patient with rudimentary non communicating horn with functional endometrium. Rudimentary horn should be kept as a differential diagnosis in young patients with dysmenorrhea and pelvic pain.