This study analyzed the accuracy of gadolinium-enhanced cardiovascular magnetic resonance (CMR) for the diagnosis of cardiac sarcoidosis (CS). The diagnosis of CS was made according to the guidelines of the Japanese Ministry of Health and Welfare (1993); CMR has not been incorporated into the guidelines, and the diagnostic accuracy of CMR for the diagnosis of CS has not yet been evaluated. We performed an analysis of 12-lead electrocardiograms (ECGs), 24-h ambulatory ECGs, echocardiograms, thallium scintigrams, and gadolinium-enhanced CMR studies in 58 biopsy-proven pulmonary sarcoidosis patients assessed for CS. The diagnostic accuracy of CMR for CS was determined using modified Japanese guidelines as the gold standard. The diagnosis of CS was made in 12 of 58 patients (21%); CMR revealed late gadolinium enhancement (LGE), mostly involving basal and lateral segments (73%), in 19 patients. In 8 of the 19 patients, scintigraphy was normal, while patchy LGE was present. The sensitivity and specificity of CMR were 100% (95% confidence interval, 78% to 100%) and 78% (95% confidence interval, 64% to 89%), and the positive and negative predictive values were 55% and 100%, respectively, with an overall accuracy of 83%. In patients with sarcoidosis, CMR is a useful diagnostic tool to determine cardiac involvement. New diagnostic guidelines should include CMR.