Incidentally detected small pancreatic cyst is a therapeutic challenge. As these lesions include a spectrum of pathologies ranging from benign lesions to malignant mucinous tumors, it is important to differentiate potential malignant mucinous cystic neoplasms (MCN) from others. However, a definitive diagnosis might be difficult, since computed tomography (CT) and magnetic resonance imaging (MRI) cannot depict the morphologic features characteristic of small MCN. This report presents a case of a small pancreatic cyst incidentally detected during medical check-up for inguinal hernia. Although the preoperative diagnosis was uncertain with CT and MRI, the diagnosis of MCN was strongly suspected because the majority of MCN tend to often occur in elderly women and the most common locations are in the pancreatic tail. Laparoscopic ultrasonography (LUS) was employed to obtain a correct diagnosis, and it showed a 16 mm cyst with characteristic features indicating a diagnosis of MCN. The patient underwent a laparoscopic distal pancreatectomy and the diagnosis of MCN was confirmed histopathologically. In conclusion, LUS allowed a timely curative resection of a small MCN in this case.