Pericardial cysts are a rare cause of mediastinal masses with an incidence of about 1 in 100,000 patients. Most of the cases are secondary to congenital incomplete fusion of the pericardial sac. More than two-thirds of pericardial cysts are located in the right cardiophrenic angle. Over 50% of pericardial cysts are asymptomatic and discovered incidentally during thoracic imaging such as chest X-ray, CT scans and transthoracic echocardiograms. Symptomatic cases commonly present with non-specific symptoms such as dyspnea, chest pain, and persistent cough. A 48-year-old female was referred for assessment of shortness of breath and atypical chest tightness for several years. The echocardiography revealed a large cystic- appearing mass presenting with slight compression of the right-atrium. A cardiac CT scan and MRI scan were performed, confirming the presence of a large pericardial cyst with no signs of complications like tamponade or pericarditis. As the patient had symptoms and cyst had compressive effects, surgical resection was done.