Abstract Objectives The goal of this study was to assess the independent and collective diagnostic value of various modalities in cardiac sarcoidosis, delineate the role of cardiac magnetic resonance (CMR), and identify patients at risk. Background Cardiac sarcoidosis is associated with increased morbidity and mortality. CMR is a key modality in the evaluation of patients with cardiac symptoms, but the complementary role of CMR to conventional tests for the diagnosis of cardiac sarcoidosis is not fully defined. Methods Patients (N = 321) with biopsy-proven sarcoidosis underwent conventional cardiac testing and CMR with late gadolinium enhancement (LGE) and were followed up for primary (composite of all-cause mortality, sustained ventricular tachycardia VT episodes, or hospitalization for heart failure) and secondary (nonsustained VT episodes) endpoints. Results Cardiac sarcoidosis was diagnosed in 29.9% of patients according to the Heart Rhythm Society consensus criteria. CMR was the most sensitive and specific test (area under the curve: 0.984); it detected 44 patients with cardiac symptoms and/or electrocardiogram (ECG) abnormalities but normal echocardiogram, as well as 15 asymptomatic patients with normal baseline testing. Echocardiography added to cardiac history and ECG did not change sensitivity of the initial screening strategy (68.8% vs. 72.9%). Despite a high positive predictive value (83.9%), echocardiography had a low sensitivity (27.1%). During follow-up, 7.2% of patients reached the primary endpoint and another 3.4% reached the secondary endpoint. LGE was and independent predictor of primary endpoints (hazard ratio: 5.68; 95% CI: 1.74 to 18.49; p = 0.004). LGE, age, and baseline nonsustained VT were independent predictors of all events. In patients with cardiac symptoms and/or an abnormal ECG, CMR increased diagnostic accuracy and independently predicted primary endpoints (hazard ratio: 12.71; 95% confidence interval: 1.48 to 109.35; p = 0.021). Conclusions Of all cardiac tests, CMR was the most valuable in the diagnosis and prognosis of cardiac sarcoidosis in a general sarcoidosis population. Echocardiography had an overall limited diagnostic value as a screening test, and an abnormal study, despite a high positive predictive value, may still need confirmation with CMR.