We report on the performance of a continuous-wave Nd:GdVO_4 laser in-band diode-pumped at 912 nm with high output power and excellent beam quality. The laser produced an output power of 19.8 W at 1063 nm with an optical efficiency of 59.3% and slope efficiency of 62.7%. The laser threshold was ∼2.04  W of the absorbed pump power, and the laser output beam quality was ≤1.2 in the horizontal and vertical directions. The strength of thermal lensing at full output power (33.4 W of absorbed power) was measured to be an average of 8.6 diopters. It is shown that thermal lensing is reduced by a factor of 2 with respect to the Nd:YVO_4 lasers, thus opening a way for further output-power scaling.