Isolated ventricular noncompaction (IVNC) is a primary cardiomyopathy characterized by a specific morphologic pattern. Patients with IVNC can develop various arrhythmic complications such as life-threatening ventricular arrhythmias, as well as heart failure or systemic embolic events. The present study was designed to comprehensively analyze the electrocardiographic (ECG) pattern at the initial diagnosis in patients with IVNC and to investigate their correlation with the clinical features and echocardiographic findings. Electrocardiograms from the initial diagnosis of IVNC were available for 78 patients from March 1995 to November 2008. The most common findings were intraventricular conduction delay (especially left bundle branch block), voltage signs of left ventricular (LV) hypertrophy, and repolarization abnormalities. An entirely normal electrocardiogram was present in 10 subjects (13%). However, no ECG findings or patterns specific for IVNC were found. A striking overlap was observed between the presence of intraventricular conduction delay (left bundle branch block, in particular), atrial conduction delay (PR interval prolongation or atrioventricular block), and prolongation of the QTc and reduced systolic LV function and LV/left atrial dilation. Moreover, patients with ECG voltage signs of LV hypertrophy more often presented with, or had a history of, systemic embolic events. In conclusion, our results have provided a comprehensive analysis of ECG findings of patients newly diagnosed with IVNC. Although intraventricular conduction delay, repolarization abnormalities, and LV hypertrophy are frequently present, no ECG patterns specific for IVNC at the first presentation with the disease were found. Whether these findings have prognostic implications needs to be investigated in long-term controlled studies.