Cubic (3C) silicon carbide (SiC) epilayers grown on Si substrates by chemical vapor deposition, characterized using transmission electron microscopy (TEM), high-resolution x-ray diffraction (HRXRD), and Raman spectroscopy, reveal the presence of biaxial in-plane strain. Defect (stacking faults, twins, dislocations) distributions revealed by TEM are correlated with peak widths obtained from HRXRD measurements and Raman shifts of the zone center longitudinal optical phonon line. TEM showed defect densities decreasing with increasing distance from SiC/Si interface as the lattice mismatch stress is relaxed. Structural defect densities show the most significant reduction within the first 2 μm of the epilayer. TEM observations were correlated with a monotonic decrease in HRXRD peak width (full width at half maximum) from 780 arc sec (1.5 μm thick epilayer) to 350 arc sec (10 μm thick epilayer). Raman spectroscopy indicates that the residual biaxial in-plane strain decreases with increasing epilayer thickness initially, but becomes essentially constant between 6 and 10 μm. Differences in the observed behavior between HRXRD and Raman spectroscopy are discussed in terms of the fundamental interactions of incident radiation with the 3C-SiC epilayers.