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The new ternary compound Y₄Ni_0.71Ag_1.29 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. Y₄Ni_0.71Ag_1.29 crystallizes with space group F (Formula presented.) 3m, cF112, a = 13.5653(8) Å, V = 2496.3(4) ų, 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. Y₄Ni_0.71Ag_1.29 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 Y₄Ni_0.71Ag_1.29 leads to an optimization of the electronic structure.