Mirena levonorgestrel intrauterine system (LNG-IUS) is a very reliable method of contraception with the failure rate comparable to sterilization. We present a case of failure of the Mirena intrauterine device in situ in a woman with twin gestational sac with positive Beta Human Chorionic Gonadotropin (β HCG) within 2 years of insertion. Although LNG-IUS is one of the most effective methods of contraception, the risks of failure should always be kept in mind and the women be appropriately counseled before its use.