Abstract: Sarcoidosis is a multisystem disorder of unknown etiology, histopathologically characterized by the formation of non-caseating epithelioid cell granulomas. Clinical manifestations are highly variable and often nonspecific, with no definitive diagnostic biomarkers currently available. The disease primarily affects the lungs and lymph nodes, while extensive systemic involvement is relatively rare. The authors report a case of a middle-aged female patient with systemic sarcoidosis who presented with exertional chest tightness and palpitations. She had a history of pulmonary sarcoidosis that had not been regularly treated. Through cardiac ¹⁸F-FDG PET/MRI and whole-body PET/CT imaging, involvement of multiple organs (including the lungs, heart, liver, spleen, bones, and lymph nodes) was identified. This case emphasizes the importance of ¹⁸F-FDG in the diagnosis of sarcoidosis, particularly the complementary value of integrated PET/MRI multimodal imaging technology in enhancing cardiac sarcoidosis diagnostic accuracy.