Idiopathic inflammatory myopathy (IIM) is a chronic autoimmune systemic disease that involves myocardium. The aim of this study is to evaluate the diagnostic value of histogram analysis of native T1 and T2 maps to identify patients with cardiac involvement in IIM. Fifteen patients with cardiac involvement in IIM and 11 normal controls were enrolled in this study. Native T1 and T2 maps were assessed by histogram analysis. Compared to the controls, the native T1 mean, median, SD and entropy were elevated significantly in IIM patients, while T2 histogram parameters showed no significant difference. A bi-parametric model including native T1 median and SD demonstrated the highest accuracy (AUC=0.93) for detecting cardiac involvement in IIM.