Using the first-principles calculation method and the special quasirandom structures approach, the authors have investigated the lattice constants as well as the direct and indirect bandgap bowing parameters, bΓ–Γ and bΓ–X, of zincblende ternary AlInN alloy. The results show that the lattice parameter of the zincblende AlInN alloy has a very small deviation from the Vegard’s rule and even exhibits a linear composition dependence. Its large direct bowing parameter bΓ–Γ is mainly ascribed to the large lattice mismatch, while its composition dependence comes from both the electronegativity difference and the structure relaxation which gives rise to the localized band edge states. The indirect bowing bΓ–X is the joint effects of the electronegativity difference and the structure relaxation, and shows weak dependent on the composition.