Percutaneous radiofrequency ablation (RFA) is widely used as an effective treatment of liver tumors. Several reported complications associated with RFA are due to thermal damage of neighboring organs. The present report presents a case of diaphragmatic hernia associated with RFA and hepatocellular carcinoma (HCC). A 72-year-old woman with S5 and S8 HCCs was treated repeatedly with RFA and transcatheter arterial chemoembolization for 3 years. After the third course of RFA to target the recurring S5 HCC, acute abdominal pain and dyspnea suddenly occurred. Contrast-enhanced computed tomography revealed intrusion of the transverse colon through the right diaphragmatic hernia. In addition, the colon was dilated and showed changes suggestive of ischemic conditions. An emergency surgery was performed to close the hernia by using non-absorbable sutures to preserve the colon. The patient was discharged without any complications 13 days after the surgery. The first-line treatment of this disease involves surgical intervention. Diaphragmatic hernia is a rare complication of RFA. The present case suggests that patients who undergo several rounds of RFA require surveillance for diaphragmatic hernias.