Previously, we briefly reported the fabrication of highly transparent yttria ceramics with fine microstructures by a facile hot-pressing method. In this article, we systematically studied the hot-pressing sintering of transparent yttria ceramics in which the effects of the ZrO₂ doping concentration, sintering temperature, and mechanical pressure on the transparency as well as the microstructures of the ceramic samples were investigated in detail. It was found that the optimal ZrO₂ doping concentration for the hot-pressed transparent yttria ceramics is 1 at.%, which is much lower than that of transparent yttria ceramics fabricated by pressureless sintering routes. An increase in both the hot-pressing temperature and the mechanical pressure effectively promoted the densification and the optical transparency of the samples doped with 3 at.% ZrO₂. However, when the mechanical pressure is too high, a substantial reduction of yttria occurs, which deteriorates the transparency of the samples.