The first manganese member in a Pb-M-In-Q system, PbMnIn(2)S(5), has been discovered by a high-temperature solid-state reaction. It adopts a Sr(2)Tl(2)O(5) structure type in orthorhombic space group Cmcm (No. 63) with a = 3.896(2) Å, b = 12.731(7) Å, c = 15.770(9) Å, and Z = 1. The structure consists of corrugated layers made by (In1/Mn1)S(6) octahedra that are further interconnected by chains of edge-sharing (In2/Mn2)S(6) octahedra into a three-dimensional framework; Pb(2+) cations are coordinated in PbS(8) bicapped triangular prisms that are face-shared along the a direction. The crystallographically distinguished octahedrally coordinated 8f and 4b sites are disordered by Mn and In atoms. Such a structure allows antiferromagnetic interactions between the high-spin Mn(2+) anions. The optical band gap is measured to be about 1.45 eV.