The magnetic properties of Ce1-xTbxMn2Ge2 (0 <= x <= 1) were investigated by means of field-cooled and zero-field-cooled magnetization measurements in the temperature range 5 K <= T <= 600 K. Earlier neutron diffraction experiments showed that Tb orders below 100 K while Ce does not order at any temperature. The substitution of Tb for Cc leads to a linear decrease in the lattice constants, and the magnetic interactions in the Mn sublattice cross over from a ferromagnetic character to an anti ferro magnetic one. At low temperatures, the Tb sublattice also orders and reconfigures the ordering in the Mn sublattice. The results are collected in a phase diagram. (C) 2005 Elsevier B.V. All rights reserved.