Interstitial pregnancy is an uncommon condition that is challenging, not only in making an accurate diagnosis, but also in the choice of treatment. Systemic methotrexate (MTX) treatment has been favored to prevent scarring of the uterus. Nevertheless, surgery is generally indicated when this treatment fails. Transvaginal aspiration of the gestational tissue has been proposed as an alternative to surgery. The authors present a case of interstitial pregnancy in which the patient failed to respond to multidose MTX treatment and was successfully treated with transvaginal sonography-guided transvaginal aspiration of the gestational tissue, thereby bypassing the risk associated with undergoing major surgery. Transvaginal aspiration of conceptive tissue may be a novel treatment for patients with unruptured interstitial pregnancy.