Completion lobectomy after radical segmentectomy is relatively rare, with no systematic evaluation of this challenging procedure. We aimed to clarify the details of this operation performed in 3 Japanese institutions. Completion lobectomy after segmentectomy in the same lobe was performed in 11 patients (9 lung cancers and 2 metastatic lung tumors) between 2007 and 2013. Surgical outcomes were analyzed retrospectively. The 11 patients accounted for 1.37% of the 805 segmentectomies performed in the 3 institutions. The reasons for completion lobectomy were postoperative complications in the remaining lobe (n = 3), positive pathological lymph node metastasis found by permanent section (n = 3), and malignancy in the remaining lobe (n = 5). The patients were divided into two groups according the interval between segmentectomy and completion lobectomy: group A (3-35 days, n = 5) and group B (56-1470 days, n = 6). There was a tendency for more severe adhesions around the hilum (p = 0.061) in group B, resulting in increased operative bleeding (p = 0.055), more usage of fibrin glue (p = 0.080), and significantly longer operative time (p = 0.036). Injury to the pulmonary arteries was experienced only in group B (3/6 cases). There was no operation-related mortality. Completion lobectomy may become more difficult approximately 5 weeks after segmentectomy, due to severe adhesions, but it can be performed safely with careful manipulation.