High-resolution absorption and stimulated-emission cross-section spectra are presented for monoclinic Nd:KGd(WO4)2 (Nd:KGW) laser crystals in the temperature range 77-450 K. At room-temperature, the maximum stimulated emission cross-section is σSE =21.4×10 -20 cm 2 at 1067.3 nm, for light polarization E || Nm. The lifetime of the 4 F3/2 state of Nd 3+ in KGW is practically temperature independent at 115±5 µs. Measurement of the energy transfer upconversion parameter for a 3 at.% Nd:KGW crystal proved that this was significantly smaller than for alternative hosts, ~2.5×10 -17 cm 3 /s. When cut along the Ng optical indicatrix axis, the Nd:KGW crystal was configured as a microchip laser, generating ~4 W of continuous-wave output at 1067 nm with a slope efficiency of 61% under diodepumping. Using a highly-doped (10 at.%) Nd:KGW crystal, the slope efficiency reached 71% and 74% when pumped with a laser diode and a Ti:Sapphire laser, respectively. The concept of an ultrathin (250 µm) Nd:KGW microchip laser sandwiched between two synthetic diamond heat-spreaders is demonstrated.