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The low fracture toughness and sensitivity to low-temperature degradation (LTD) are the primary reasons for the suboptimal long-term performance of dental zirconia. Composite ceramics of zirconia have gained popularity due to their ability to combine the benefits of various reinforcements. In this study, Al2O3–SrAl12O19–3Y/4Y/5Y–ZrO2composite ceramics were fabricated using the Pechini method, and the optimal sintering temperature and time were investigated. The relative density, microstructure, grain size, mechanical properties, and LTD resistance of the samples were characterized. The results indicated that the composite achieved optimal performance when sintered at 1500 °C for 3 h. Al2O3and SrAl12O19primarily influence the properties of the zirconia composite ceramics by modulating their density and grain size. With an increase in the content of Al2O3and SrAl12O19, the relative density first increases and then decreases, while the grain size exhibits an inverse trend, resulting in an initial increase followed by a decrease in fracture toughness. Additionally, the rate of increase in the m-phase fraction of the zirconia composite slowed down, but it reached a similar level after 64 h of LTD. The incorporation of 8 vol% Al2O3and 8 vol% SrAl12O19into 3Y–ZrO2resulted in a ceramic composite with the highest fracture toughness values and acceptable LTD sensitivity, measured at 5.23 ± 0.25 MPa m1/2and 48.35 ± 5.70% m-phase (LTD 64 h), respectively. This composite also exhibited high bending strength (990.09 MPa) and hardness (16.52 GPa), making it a promising alternative to conventional 3Y-TZP ceramics commonly used in dentistry.