We sought to assess the value of non-contrast enhanced transthoracic harmonic echocardiography (TEE) for the visualization of left ventricular thrombi in 34 patients with cardiomyopathy. Results were compared to contrast-enhanced magnetic resonance imaging as reference standard. Maximal thrombus size was quantified with both modalities. Magnetic resonance imaging demonstrated thrombi in 15 patients. In these subjects echocardiography was negative in seven patients. Thrombi were excluded in 19 patients with magnetic resonance while echocardiography was deemed positive in 5 subjects. Thrombus size by ce-CMR was not different for clots visualized or not visualized by echocardiography (P = 0.71). Moreover, observer agreement was superior for ce-CMR (kappa = 0.94) as compared to TTE (kappa= 0.71). Non-contrast-enhanced harmonic TTE has limited value for the visualization of thrombi in patients with cardiomyopathy.