Background Excessive trabeculation is present in isolated left ventricular noncompaction (LVNC) and dilated cardiomyopathy (DCM), which sometimes makes the differentiation between these two difficult. Fractal dimension (FD) is a unitless measure value of how completely the object fills space, which can assess the extent of myocardial trabeculae quantitatively. Purpose To compare the trabeculae features and myocardial strain derived from cardiac MR between LVNC and DCM. Study Type Respective case-control series. Population In all, 35 LVNC patients and 30 DCM patients were enrolled, and 20 healthy volunteers were selected as a control group. Field Strength/Sequence 5 T with 8-channel phased-array cardiac receiver coil including steady-state free precession cine imaging. Assessment The degree of left ventricular trabeculation was evaluated by a semiautomatic tool based on fractal analysis. Myocardial deformation was assessed by feature tracking. Statistical Tests Independent samples Student's t-test, Mann-Whitney U-test, receiver operating characteristics (ROC) curves, and Spearman's rank coefficient were conducted. Results Max apical FD and mean global FD were higher in the LVNC group than in the DCM group (1.433 +/- 0.074 vs. 1.341 +/- 0.062, P < 0.001; 1.323 +/- 0.036 vs. 1.267 +/- 0.041, P < 0.001, respectively). For diagnosing LVNC, max apical FD was 1.392 (area under the curve [AUC] = 0.881, 95% confidence interval [CI]: 0.804-0.957), and the cutoff value of mean global FD was 1.283 (AUC = 0.895, 95% CI: 0.828-0.961). The global peak longitudinal strain value of the left ventricle (GPLS) showed significant differences between the LVNC group and DCM group [-6.49 (-11.41, -4.90) vs. -4.61 (-5.87, -3.61), P = 0.006]. The diagnostic accuracy for LVNC is highest when using FDs in coordination with GPLS (AUC = 0.93, 95% CI: 0.86-0.98, P < 0.001). Data Conclusion Fractal analysis provides a quantitative measurement of myocardial trabeculation. The combination of fractal analysis with myocardial strain provides a novel biomarker in distinguishing LVNC from DCM. Technical Efficacy Stage: 2 J. Magn. Reson. Imaging 2019;50:153-163.