Background. In 2017, the General Rules for the Clinical and Pathological Classification of Lung Cancer were revised, and the classification of minimally invasive adenocarcinoma was added. We herein report a case in which lymph node metastasis was detected despite the tumor being diagnosed as a minimally invasive adenocarcinoma. Case. An 80-year-old woman was referred to our department after computed tomography (CT) revealed a suspected lung cancer nodule in the upper right lung lobe. CT showed a solid 2.3-cm nodule with an air bronchogram and a pleural indentation in the upper lobe (S3) of the right lung. Positron emission tomography (PET)-CT revealed the accumulation of fluorodeoxyglucose in the nodule (maximum standardized uptake value=4.5). No obvious lymph node enlargement was observed on CT, and no abnormal fluorodeoxyglucose accumulation suspected as distant metastasis was observed on PET-CT. Despite the lack of a histological diagnosis, we strongly suspected lung cancer and made a preoperative diagnosis of c-T1cN0M0 c-stage IA3. We therefore performed thoracoscopic right upper lobectomy and ND2a-1 lymph node dissection and obtained a rapid intraoperative diagnosis of lung adenocarcinoma. A histopathological examination also revealed lung adenocarcinoma. The 1.8-cm tumor had a predominantly lepidic pattern and an infiltrative diameter of <5 mm and was therefore diagnosed as pT1mi. Lobar lymph node #12u was positive for metastasis. We thus made a diagnosis of pN1. As there is no stage that corresponds to T1miN1M0 in the 8th edition of the General Rules for the Clinical and Pathological Classification of Lung Cancer, postoperative adjuvant chemotherapy was performed for T1aN1M0 stage IIA in accordance with the 7th edition. At the time of writing this report, the patient was alive at 51 months after surgery without recurrence. Conclusion. We experienced a very rare case of minimally invasive adenocarcinoma accompanied by a lymph node metastasis.