We are reporting on a case of lymphadenopathy after surgery for rectal cancer. The case was a 66‒year‒old female. Laparoscopic high anterior resection(D3 dissection)was performed for rectal cancer(pT1bpN0M0, pStage Ⅰ)in April 2018, and she was followed up with on an outpatient basis. In July of the same year, a painless mass had formed in the right groin. An abdominal contrast‒enhanced CT showed lymph node swelling around the right groin and external iliac artery, but the tumor markers, CEA 2.3 ng/mL and CA19‒9 <2 U/mL, were within the standard values. An inguinal lymph node biopsy was performed during the same month. Pathological examination revealed no cancer cells and formation of epithelioid granuloma with giant cells. There was no suspicion of systemic sarcoidosis based on the test results and clinical findings. From the above, the patient was diagnosed with sarcoid reaction due to the tumor. Abdominal contrast‒enhanced CT scan 2 months after the biopsy showed lymph node shrinkage and there was no recurrence 2 years after the biopsy.