The effect of the partial substitution of Al for Ag in the glass forming ability (GFA) of the Zr 57.52 Co 21.24 Al 21.24-x Ag x (x = 8, 10, 12, and 14 at. %) family alloy are reported and discussed. Cylindrical and conical ingots were obtained using the suction casting technique. It was found that the Zr 57.52 Co 21.24 Al 9.24 Ag 12 alloy showed a glassy structure, with a critical glassy diameter, D c , of 2 mm and ∆T x = 41 K. The bulk metallic glass Zr 57.52 Co 21.24 Al 9.24 Ag 12 alloy was examined using scanning electron microscopy, differential thermal analysis and mechanical compression test. This alloy showed a Young´s modulus (E) of 76.4 GPa and yield strength (σ y ) of 1.58 GPa. The Glass Forming Ability of the Zr 57.52 Co 21.24 Al 9.24 Ag 12 was explained in terms of the topological model of dense packed clusters and kinetic fragility index of the alloy.