The crystal structures of three ternary Ni-Zn borides have been elucidated by means of X-ray single-crystal diffraction (XSC) and X-ray powder diffraction techniques (XPD) in combination with electron microprobe analyses (EMPA) defining the Ni/Zn ratio. Ni21Zn21B24 crystallizes in a unique structure type (space group I4/mmm; a = 0.72103(1) am and c = 1.42842(5) nm; R-F(2) = 0.017), which contains characteristic isolated cages of B-20 units composed of two corrugated octogonal boron rings, which are linked at four positions via boron atoms. The B-20 units appear to have eight-membered rings on all six faces like the faces of a cube. Each face is centered by a nickel atom. The six nickel atoms are arranged in the form of an octahedron nested within the B-20 unit. Such a boron aggregation is unique and has never been encountered before in metal boron chemistry. The crystal structure of Ni12ZnB8-x (x = 0.43; space group Cmca, a = 1.05270(2) nm, b = 1.45236(3) nm, c = 1.45537(3) tins; R-F(2) = 0.028) adopts the structure type of Ni12AlB8 with finite zigzag chains of five boron atoms. The compound Ni3ZnB2 crystallizes in a unique structure type (space group C2/m, a = 0.95101(4) nm, b = 0.28921(4) nm, c = 0.84366(3) nm, beta = 101.097(3)degrees, and R-F(2) = 0.020) characterized by B-4 zigzag chain fragments with B-B bond lengths of 0.183-0.185 nm. The Ni3ZnB2 structure is related to the Dy3Ni2 type.