Background Pericardial hematoma is blood accumulation in the pericardial space. Although rare, it could arise in various conditions, such as after cardiac surgery. Clinical diagnosis of pericardial hematoma is implausible; thus, cardiac imaging plays a pivotal role in identifying this condition. We presented a case of multiple pericardial hematomas, which was found as an incidental finding in post-cardiac surgery evaluation. We highlighted the diagnostic challenge and the key features of multi-modality cardiac imaging in pericardial hematoma evaluation. Case presentation An asymptomatic, 35-years old male, who underwent surgical closure of secundum atrial septal defect (ASD) one month ago, came for routine transthoracic echocardiography evaluation. An intrapericardiac hematoma was visualized at the right ventricle (RV) 's free wall side. Another mass with an indistinct border was visualized near the right atrium (RA). This mass was suspected as pericardial hematoma differential diagnosed with intracardiac thrombus. Cardiac computed tomography (CT) scan showed both masses have an attenuation of 30–40 HU; however, the mass's border at the RA side was still not clearly delineated. Mild superior vena cava (SVC) compression and multiple mediastinal lymphadenopathies were also detected. These findings are not typical for pericardial hematomas nor intracardiac thrombus; hence another additional differential diagnosis of pericardial neoplasm was considered. We pursued further cardiac imaging modalities because the patient refused to undergo an open biopsy. Single-photon emission computer tomography (SPECT)/CT with Technetium-99 m (Tc-99 m) macro-aggregated albumin (MAA) and Sestamibi showed filling defect without increased radioactivity, thus exclude the intracardiac thrombus. Cardiac magnetic resonance imaging (MRI) reveals intrapericardial masses with low intensity of T1 signal and heterogeneously high intensity on T2 signal weighted imaged and no evidence of gadolinium enhancement, which concluded the diagnosis as subacute pericardial hematomas. During follow-up, the patient remains asymptomatic, and after six months, the pericardial hematomas were resolved. Conclusion Pericardial hematoma should be considered as a cause of pericardial masses after cardiac surgery. When imaging findings are atypical, further multi-modality cardiac imaging must be pursued to establish the diagnosis. Careful and meticulous follow-up should be considered for an asymptomatic patient with stable hemodynamic.