The effects of replacing Pr by Lu on the magnetic behaviour and structures of Pr1−xLuxMn2Ge2 (x = 0.2,x = 0.4) have been investigated using x-ray diffraction, Mössbauer spectroscopy, magnetization and neutron diffraction measurements. The substitution of Lu for Pr leads to a decrease in the lattice constants a, c and the unit cell volume V at room temperature with this contraction of the unit cell resulting in modifications of the Pr1−xLuxMn2Ge2 magnetic structures. Four and five magnetic phase transitions—linked primarily with temperature driven changes in the intralayer Mn–Mn separation distances—have been detected within the temperature range 4.5–550 K for Pr0.8Lu0.2Mn2Ge2 and Pr0.6Lu0.4Mn2Ge2, respectively, with re-entrant ferromagnetism being detected around TCPr~31 K for Pr0.6Lu0.4Mn2Ge2. It was found that TCinter and TCPr increase with increasing applied field while TNinter decreases for Pr0.6Lu0.4Mn2Ge2, indicating that the canted antiferromagnetic AFmc region contracts with increasing field. The Debye temperatures for Pr1−xLuxMn2Ge2 with x = 0.2 and 0.4 were evaluated as θD = 320 ± 40 K and θD = 400 ± 20 K respectively from the temperature dependence of the average isomer shift. The magnetic structures of both compounds have been determined by means of neutron diffraction measurements over the temperature range 3–300 K with formation of the Fmi magnetic state below Tc/c = 192 K for Pr0.8Lu0.2Mn2Ge2 and the occurrence of re-entrant ferromagnetism below TCPr = 31 K for Pr0.6Lu0.4Mn2Ge2 being confirmed.