Abstract Laser-induced incandescence (LII) of a surface layer of GaSb/InxGa1−xSb/GaSb (x = 0.1) sandwich heterostructure is investigated in the visible spectral region under irradiation by the third harmonic of radiation of a Q-switched YAG:Nd3+ laser. Within the laser-induced hot spot on the irradiated surface, strong granularity of LII is observed. The experiments revealed that the intensity of surface-integrated LII in the InxGa1−xSb region is twofold larger than in the GaSb regions of the investigated structure; this fact is interpreted as consequence of difference in thermal conductivities of GaSb and InxGa1−xSb. Computer simulations were performed for LII of laser-melted surface layers. The results of simulations are in agreement with the experimental data.