Background: Primary pericardial mesothelioma is an extremely rare tumor, and early identification and accurate diagnosis may improve its clinical outcome. Case presentation: In this study, we reported a case of a 70-year-old woman who presented with dyspnea. Conventional transthoracic echocardiography showed massive pericardial effusion. Contrast-enhanced ultrasonography revealed a hyper-enhancing mass in the pericardium. Further imaging methods, including cardiac MRI and positron emission tomography/computed tomography, showed invasion of the pericardial mass into the adjacent tissues and distant metastases. Pathologic examination of a puncture biopsy specimen finally confirmed the diagnosis of PPM. Conclusion: Pericardial masses are difficult to detect when a large amount of pericardial effusion is present and the mass is small. The combination of multiple modalities plays a meaningful role in identifying PPM.