Since cardiac sarcoidosis (CS) leads to substantial morbidity and sudden death, early diagnosis and appropriate management are crucial for patients with CS. Echocardiography used to be considered a useful diagnostic tool for patients with CS, but CS may clinically present as dilated cardiomyopathy (DCM). Our objective was to investigate whether a novel three-dimensional (3-D) speckle-tracking strain can identify patients with CS more accurately. We studied 23 CS patients with an ejection fraction (EF) of 46 ± 10 %, and 16 EF-matched patients with DCM (EF 45 ± 11 %). Global radial (GRS), circumferential (GCS) and longitudinal (GLS) strain was assessed using 3-D speckle-tracking system. GRS of patients with CS was significantly lower than that of patients with DCM (18.5 ± 8.4 vs. 28.5 ± 8.3 %, p < 0.01), but GCS and GLS in patients with CS and DCM were similar. GRS ≦ 21.1 could differentiate CS from DCM with a sensitivity of 70 %, specificity of 88 % and area under the curve of 0.79. An additional noteworthy findings was that, patients with CS showed more negative radial strain curves than did those with DCM (1.7 ± 2.3 vs. 0.1 ± 0.5, p < 0.01). In conclusion, 3-D speckle-tracking radial strain shows good potential to distinguish CS from DCM. Our observations can thus be expected to have clinical implications for management of CS patients.