[en] EPR measurements have been made at room temperature on Tl₂ZnF₄ crystals doped with Gd³⁺ and co-doped with Gd³⁺ and Li⁺. For crystals doped only with Gd³⁺, a spectrum with tetragonal symmetry (A centre) is observed. For co-doped crystals new spectra with tetragonal (B centre) and monoclinic (C centre) symmetries are observed in place of the spectrum of the A centre. The A centre is identified as the substitutional Gd³⁺ ion at a Zn²⁺ site in six-fold coordination without any local charge compensation in its immediate neighbourhood. On the basis of spin Hamiltonian separation analysis, the separated parameter b_2a(1) for the C centre has a value close to the b₂⁰ parameter for the B centre. The B and C centres in co-doped crystals are ascribed to a Gd³⁺ ion substituted for a Tl⁺ site in nine-fold coordination, where the divalent excess positive charge on Gd³⁺ is compensated by a Li⁺ ion at the Zn²⁺ site along the c axis. For the C centre, another association with a Li⁺ ion is found at the nearest Zn²⁺ site along the [111] direction. The other separated parameter b_2a(2) for the C centre has an opposite sign and six times the magnitude of b₂⁰ for the Gd³⁺ centre with trigonal symmetry along the [111] direction in RbCaF₃. The large magnitude negative value may be due to the deviation of the ligands toward the Li⁺ ion at the nearest Zn²⁺ site