The electronic structures, magnetic properties and half-metallicity in Zr(2)IrZ (Z = Al, Ga, In) alloys with the Hg2CuTi-type structure were systematically investigated by using the first-principle calculations. Zr(2)IrZ (Z = Al, Ga, In) alloys are predicted to be half-metallic ferrimagnets which are quite robust against hydrostatic strain and tetragonal deformation. The total magnetic moment of Zr(2)IrZ (Z = Al, Ga, In) alloys mainly originates from the 4d electrons of Zr atoms and follows the conventional Slater-Pauling rule: M-t = Z(t) - 18. (Mt is the total magnetic moment per unit cell and Z(t) is the valence concentration). The origin of the band gap for Zr(2)IrZ (Z = Al, Ga, In) alloys is also well studied. Unconventionally, Zr2Ir-based alloys contain element with 5d valence electrons, which implies a wider field to search for new half-metallic materials. (C) 2015 Elsevier B.V. All rights reserved.