Four members of a new series of oxides of nominal stoichiometry NdMn2–xRuxO5 (x = 0.1, 0.2, 0.4, 0.5) have been prepared in polycrystalline form by wet‐chemistry procedures followed by thermal treatment at 1000 °C. NdMn2–xRuxO5 materials are isostructural with NdMn2O5. Their crystal structures have been refined from XRD data and, for the x = 0.5 oxide, from NPD data in the space group Pbam. The crystal contains infinite chains of (Mn,Ru)4+O6 octahedra sharing edges, linked together by dimeric (Mn)3+O5 square pyramidal units and NdO8 polyhedra. There is a slight anti‐site disordering effect, implying that some Ru cations are introduced at the pyramidal positions. For x = 0.5, the crystallographic formula is Nd3+(Mn4+0.572(4)Ru4+0.428(4))oct(Mn3+0.964(8)Ru3+0.036(8))pyrO4.92(4). The abrupt contraction of the c axis for x = 0.5, together with the short (Mn,Ru)−(Mn,Ru) distances (2.60 Å) observed within the chains of octahedra suggest the presence of Ru–Ru metal bonding for this composition. The magnetic properties are characteristic of spin‐glasses, as confirmed by ac susceptibility measurements.