Coherent InxAl1−xN (x = 0.15 to x = 0.28) films were grown by metalorganic chemical vapor deposition on GaN templates to investigate if the films obey Vegard’s Law by comparing the film stress-thickness product from wafer curvature before and after InxAl1−xN deposition. The In composition and film thickness were verified using atom probe tomography and high resolution X-ray diffraction, respectively. Ex-situ curvature measurements were performed to analyze the curvature before and after the InxAl1−xN deposition. At ∼In0.18Al0.82N, no change in curvature was observed following InAlN deposition; confirming that films of this composition are latticed matched to GaN, obeying Vegard’s law. The relaxed a0- and c0- lattice parameters of InxAl1−xN were experimentally determined and in agreement with lattice parameters predicted by Vegard’s law.