Abstract: An experimental study aimed at developing the method of the spontaneous synthesis of InGaN/GaN nanowires formed as radial heterostructures by molecular-beam epitaxy is reported. By means of electron microscopy, it is shown that a wedge-shaped crack can be formed at an In content x = 0.4 and 0.04 in the core and shell, respectively. On the basis of the model of internal structural stresses, a formula is proposed to estimate the critical dimensions and composition for the formation of cracks in nanowires. Comparison of the estimates with the experimental morphology data shows good agreement between them.