Repeated cytology of pancreatic juice obtained by endoscopic nasopancreatic drainage (ENPD) tube has been highlighted as an early diagnostic method for small pancreatic cancer, including carcinoma in situ. We report two cases of early-stage pancreatic cancer diagnosed using repeated cytology; both cases underwent curative resection. No significant masses were found on conventional imaging in either case, with only pancreatic duct strictures being observed. ENPD tubes were placed to collect pancreatic juice in both cases. In case 1, two of five pancreatic juice samples showed adenocarcinoma. Therefore, distal pancreatectomy was performed, and a PanIN3 grade neoplasm (carcinoma in situ) was identified at the branch duct near the distal stricture. In case 2, two of seven pancreatic juice samples (collected during the second tube placement) showed adenocarcinoma. Therefore, distal pancreatectomy was performed, and a PanIN3 neoplasm was identified primarily in the pancreatic duct at a narrow section with fibrosis. Partial microinvasion (<1 mm) was observed at the branch duct. Repeated cytology of pancreatic juice obtained by ENPD tube is effective for early diagnosis of pancreatic cancer, especially in cases without mass formation. However, some issues, including the appropriate number of samples, should be addressed in large prospective studies.