The new ternary compound Y4Ni0.71Ag1.29 has been prepared by arc melting the elements under inert atmosphere. Subsequent annealing at 800°C for 2 weeks yielded crystals of sufficient quality for structure determination by single-crystal X-ray diffraction. Y4Ni0.71Ag1.29 crystallizes with space group F (Formula presented.) 3m, cF112, a = 13.5653(8) Å, V = 2496.3(4) Å3, Z = 16. Its crystal structure represents a ternary, disordered variant of the Gd4RhIn type, with Ni positions corresponding to the Rh sites and Ag positions to the In sites of the prototype. Y4Ni0.71Ag1.29 is the first representative of this type with three transition metals, exhibiting an unique distribution of its components. Electronic structure calculations were performed for an idealized stoichiometric Y4NiAg to understand the origins of nonstoichiometry, which reveal that adjusting the composition to Y4Ni0.71Ag1.29 leads to an optimization of the electronic structure.