The structural and magnetic properties of the polycrystalline Tb1-xNdxMn2Si2 (0less than or equal toxless than or equal to1) compounds were studied by means of X-ray powder diffraction, AC susceptibility and differential scanning calorimetry (DSC). All compounds investigated crystallize in the body-centered tetragonal ThCr2Si2-type structure with the space group 14/mmm. Substitution of Nd for Tb leads to a linear increase of the lattice constants and the unit cell volume. The lattice constants and the unit cell volume obey Vegard's law. At low temperatures, the rare-earth sublattice orders and reconfigures the ordering in the Mn sublattice. The samples with x=0.2, x=0.4 and x=0.6 exhibit spin reorientation phenomenon below T-C(RE) and at about 200 K, AC susceptibility curve of these samples has a cusp denoting the Neel temperature T-N1(Mn). The Neel temperature T-N2(Mn) determined by DSC technique decreases linearly with increasing Nd content x. The results are collected in the x-T magnetic phase diagram. (C) 2004 Elsevier B.V. All rights reserved.