Ciliated foregut cysts (CFCs) are rare masses that develop from the tissues which remain from embryological foregut development. In the literature, about a hundred cases have been described in various organs so far. Although rare, there is a risk of development of squamous cell carcinoma from these cysts that typically bear benign features. Prognosis following the development of carcinoma is poor. A female case presented with upper quadrant pain and was sent to radiology for US examination of the abdomen. In 2010, a cyst which was about 5 mm in size was detected on the wall of the gall bladder. In subsequent US, the lesion reached 7 mm in diameter and a shape protruding to the lumen was included in the findings; therefore, it was decided to operate. The mass was diagnosed as a CFC of the gallbladder. We determined that the lesion had the smallest dimension noted in the literature. Congenital gallbladder cysts are detected rather rarely. The US characteristics are enough to make a definitive diagnosis, and the other imaging methods therefore remain unnecessary. Treatment using a laparoscopic surgical method is the first preference.