Comprehensive studies of electroluminescence of InAs/InAsSb/InAsSbP heterostructures with different fractions of Sb in narrow-gap InAsSb layers were performed. Electroluminescent properties of the heterostructures were investigated in a wide range of both forward and reverse biases at temperature T = 77 K. It was found that in the different parts of the heterostructures, radiative recombination proceeds via interband and interface mechanisms, which manifests in the presence of two emission bands at different wavelengths in the electroluminescence spectra recorded under the forward bias. The recombination mechanisms were explained using schematic band diagrams of the heterostructures calculated for T = 77 K and both directions of the external bias.