Continuous-wave laser action of a Tm-doped GdLiF(4) (GLF) crystal pumped by a laser diode is reported at room temperature. A comparative analysis of laser performance using GLF crystals with doping concentrations of 8 at. % and 12 at. % of Tm(3+) has been carried out. A maximum output power of 1.47 W with 57% slope efficiency and a wide tunability range from 1826 to 2054 nm have been obtained at 8% Tm doping level.