The room‐temperature thermal conductivity of III‐V compounds is analyzed. The phenomenological approach of Abeles is applied to take into account disordered structure of ternary and quaternary alloys. The procedure is used for the In1−xGaxAsyP1−yquaternary alloy. The approximate analytical expression for this case is derived. A more exact method of the calculations is also proposed. It enables presenting the thermal conductivity and the thermal diffusivity for both the InP lattice‐matched and GaAs lattice‐matched In1−xGaxAsyP1−yalloys as a function of their composition.