The sinterability of manganese-doped 8 mol% yttria-stabilized zirconia ranging from 0.5–5 wt% was investigated. The role of dopants in the samples was studied in terms of phase stability, microstructures, and mechanical properties. Accordingly, 0.5, 1, 3, and 5 wt% manganese were doped into yttria-stabilized zirconia and heated at temperatures ranging from 1300 °C to 1550 °C. The study revealed that the milling process reduced powder particle size from 0.54 μm to 0.16 μm. The grain size of the samples increased with increasing sintering temperature, and adding manganese dopants promoted further grain growth. When sintered at 1450 °C, 3 wt% manganese enhanced the densification of the sample to a relative density of 95.8% and Vickers hardness peaked at 14.4 GPa. The samples with manganese dopants exhibited fracture toughness values of 4.1–4.6 MPa · m^1/2 when sintered at temperatures above 1450 °C, regardless of dopant content. Zircon was found on the surface of the sintered sample with over 3 wt% manganese addition but did not disrupt zirconia phase stability. The study showed that the mechanical properties of yttria-stabilized zirconia improved when manganese dopants were added.