The crystal structure of [Mn-3(Hsaladhp)(2)(acetato)(2)(5-Cl-salicylato)(2)](n) shows it to be a polymeric chain with the trimeric Mn(III)-Mn(II)-Mn(III) units bridged by phenolate groups of the Schiff-base ligand. Variable-temperature magnetic susceptibility measurements indicate the manganese ions within the trimeric unit are antiferromagnetically exchange coupled yielding an S = 3/2 ground state. The magnetic data also provide evidence for a weak antiferromagnetic intertrimer exchange interaction, indicating the compound behaves as an S = 3/2 linear chain at low temperatures.