The synthesis, crystal structure and magnetic properties of [Mn(III)L(H2O)2]+ClO4 −, 1 [L = N,N′-bis(rac-3,5-dichlorosalicylidenato)-1,2-diaminopropane] are reported. Single crystal X-ray diffraction studies showed the structure to consist of [MnL(H2O)2]+ octahedra, with trans-coordinated water molecules, which are linked into infinite helices by hydrogen bonds. The distorted octahedral manganese(III) centre contains an N2O2O′2 coordination sphere made up of the Schiff base ligand in the equatorial plane. In the axial direction, an elongation of the trans Mn-Owater bonds to 2.165(2) and 2.187(2) Å is observed. Such elongations are typical of d4 systems but in this case may also be attributed to the poorer donor power of the water molecules.