This study retrospectively evaluated the computed tomography (CT) findings of idiopathic multicentric Castleman disease (iMCD) at a single center and compared the CT findings of iMCD-TAFRO with those of iMCD-non-TAFRO. CT images obtained within 30 days before diagnostic confirmation were reviewed for 20 patients with iMCD (8 men and 12 women, mean age 52.8 ± 12.3 years, range 25-74 years). Twelve patients were diagnosed with iMCD-TAFRO, five with iMCD-idiopathic plasmacytic lymphadenopathy, and three with iMCD-not otherwise specified. CT images revealed anasarca and lymphadenopathy in all 20 patients. The iMCD-TAFRO group showed significantly higher frequencies of ascites (100% vs. 37.5%, P = 0.004), gallbladder wall edema (75.0% vs. 12.5%, P = 0.020), periportal collar (91.7% vs. 25.0%, P = 0.004), and anterior mediastinal lesions (non-mass-forming infiltrative lesions) (66.7% vs. 12.5%, P = 0.028). Para-aortic edema tended to be more frequent in patients with the iMCD-TAFRO group (83.3% vs. 37.5%, P = 0.062), while the absence of anterior mediastinal lesions tended to be more frequent in the iMCD-non-TAFRO group (16.7% vs. 62.5%, P = 0.062). These CT findings may have clinical implications for improving the accuracy and speed of iMCD diagnosis and differentiating iMCD-TAFRO from other subtypes.