Mechanical properties of Ag⁺/Na⁺ ion-exchanged aluminosilicate glasses are investigated. The aluminosilicate glass samples with the thickness of 1 mm and homogeneous Ag⁺/Na⁺ concentrations were prepared via the ion exchange in the molten salt at 450°C and the following post-heating in the ambient atmosphere. Measured Young's modulus, Vickers hardness and fracture toughness in a dry nitrogen atmosphere change nonlinearly with increasing Ag/(Ag+Na) ratio, and show the maximum values, 75 GPa, 560 kg/mm² and 0.84 MN/m^3/2 around Ag/(Ag+Na)=50%, respectively. Fully exchanged glass shows the same modulus 70 GPa as that of the mother glass and the smallest hardness and toughness, 500 kg/mm² and 0.74 MN/m^3/2, respectively. The calculated yield stress decreases from 2.59 GPa to 2.30 GPa with increasing Ag/(Ag+Na) at more than 60% region. Coexistence of Ag⁺/Na⁺ induces mixed cation effect, and gives a maximum to the elastic modulus at Ag : Na=1 : 1. Additionally, the yield stress of glass is decreased with increasing Ag⁺ concentration by the difference of the effect on Al-O-Si network between Ag⁺ and Na⁺.