The vacancy ordered halide perovskites Tl2WX6 (X = Cl, Br and I) were investigated using first principles calculations along with Boltzmann theory to understand its structural, electronic, magnetic and spin based transport properties. The crystal structure of Tl2WX6 (X = Cl, Br and I) is optimized using Generalized Gradient approximation-Perdue Burke Ernzerhof sol (GGA-PBEsol) approximation where the ferromagnetic state is found to be stable. The Goldschmidt's tolerance factor confirms the cubic phase stability. The mechanical characteristics are demonstrated by Young's modulus, Bulk modulus, Shear modulus, and Poisson's ratio which shows that Tl2WX6 (X = Cl and Br) are brittle and Tl2WI6 is ductile. According to the spin polarized band structure calculation the Tl2WX6 (X = Cl, Br, and I) are half metallic ferromagnetic in nature, where the material acts like a metal in the majority spin channel and as a direct band gap semiconductor in the minority spin channel. The estimated band gaps of Tl2WCl6, Tl2WBr6 and Tl2WI6 are 2.77 eV, 1.885 eV, and 0.89 eV respectively. The electronic structures reveal the half metallic gap of Tl2WX6 (X = Cl, Br and I) as 0.481 eV, 0.413 eV and 0.279 eV respectively. The magnetic behaviour of the materials is solely due to 5d states of W and the double exchange mechanism resulting in an integer magnetic moment of 2.00 μB making them appropriate for spintronic applications. Moreover the evaluation of spin based transport properties of Tl2WX6 (X = Cl, Br and I) alloys exhibit high power factor, ultra low thermal conductivity and high ZT which are ideal characteristics for a good thermoelectric material.