Introduction: Several cases of Morgagni hernia have recently been treated with laparoscopic mesh repair, which is reported to have fewer complications and to be less invasive. Here we describe a case of a laparoscopic Morgagni hernia repair treated with mesh that progressed to heart failure due to pericardial effusion 2 months after hospital discharge. Case Presentation: A 78-year-old woman was incidentally found to have a Morgagni hernia during a routine chest X-ray. The laparoscopic Morgagni hernia repair was performed using Composix mesh○R and an ENDOPATH○R EMS Stapler. The Composix mesh○R was gently attached to the surface of the diaphragm using the ENDOPATH○R EMS Stapler. She was discharged from the hospital on the 7th postoperative day without any adverse events. However, 2 months later, she developed dyspnea due to heart failure secondary to a pericardial effusion. Pericardial drainage was performed during her hospitalization, and she was discharged 7 days later. No recurrence of either the pericardial effusion or the Morgagni hernia has been detected since the pericardial drainage Conclusion: Clinicians may need to be aware of the risk of pericardial effusion in these cases, even if there has been no damage to the diaphragm or epicardium.