Polyoxomolybdates tend to re-agglomerate to β-octamolybdate upon reaction with Ag+ under hydrothermal conditions and in organic solvents. Consistent with this tendency, a new coordination polymer [Ag(PhCN)(thb)]4[β-Mo8O26](PhCN)2 (thb = theobromine) (1) was obtained and characterized by single crystal XRD, powder XRD, DTA/TG, IR, UV/Vis, and elemental analysis. 1 is a one-dimensional coordination polymer, in which octamolybdate anions are joined by [Ag(PhCN)(thb)]+ cations along the crystallographic a axis. A firm network of intermolecular interactions, especially between self-pairing thb ligands, interlinks these chains. Salt 1 is turned into MoO2 and Ag upon thermolysis in an intramolecular redox reaction.