Amorphous metallic alloys possess high strength characteristics, which are superior to crystalline materials. Here we report an influence of Sc addition on glass-forming ability, glass-transition behavior, supercooled liquid region, and mechanical properties of an Al84Y9Ni5Co2 glassy alloy. This paper also aims to present a promising (Al0.84Y0.09Ni0.05Co0.02)95Sc5 amorphous alloy. This alloy has an ultrahigh tensile fracture strength exceeding 1500 MPa, which surpasses those for all the other Al-based fully crystalline and amorphous alloys reported to date, in addition to high Young’s modulus of 78 GPa. The fracture surface of this new alloy exhibited vein pattern typical for amorphous alloys with good ductility, and multiple shear bandswere observed on the lateral surface. The ultrahigh tensile strength of the (Al0.84Y0.09Ni0.05Co0.02)95Sc5 amorphous alloy results from an increase in the interatomic constraint force by the addition of Sc, an element having highly negative enthalpy of mixing with Al, Ni, and Co and the highest chemical affinity with Al among the alloying elements.