An efficient diode-pumped $\mathrm{Yb}\text{:}{\mathrm{Y}}_3{\mathrm{Ga}}_5{\mathrm{O}}_{12}$ (Yb:YGG) laser was demonstrated by using a high-quality Yb:YGG crystal grown by the optical floating zone method. Continuous-wave laser power up to $2.65\mathrm{W}$ had been obtained under an incident pump power of $6.71\mathrm{W}$ at $970\mathrm{nm}$ , corresponding to an optical-to-optical efficiency of 39.5% and maximum slope efficiency of 84.5%. A modeling calculation of the Yb:YGG laser was also performed, and the theoretical results were consistent with the experimental results.