Ta3Ru5B2, Zr2.86(5)Ru5.14(5)B2, and Hf2.83(2)Ru5.17(2)B2 have been successfully synthesized as polycrystalline powders as well as single crystals and characterized by powder and single-crystal X-ray diffraction and EDX analysis. Furthermore, their electronic structures and bonding characteristics have been analyzed by DFT calculations. The three phases are isotypic and crystallize with a Ti3Co5B2-type structure (space group P4/mbm). Their electronic densities of states, which all possess a large pseudogap at the Fermi level, closely follow the rigid band model. Bonding analyses indicated that Ru–B and Ru–M (M = Zr, Hf, Ta) heteroatomic interactions are mainly responsible for their structural stability and that the homoatomic M–M interactions behave differently when connecting either two tetragonal or two pentagonal Ru prisms at the same distance.