This article describes a temperature-and photo-induced phase transition in rubidium manganese hexacyanoferrate, RbMn[Fe(CN) 6 ]. This compound displays a drop in the magnetic susceptibility at 225 K (=T 1/2โ ) and an abrupt increase in the magnetic susceptibility at 300 K (=T 1/2โ ) in the cooling and warming processes, respectively. This phase transition is accompanied by a structural change from cubic (F 43m) to tetragonal (I 4m2). The high-temperature (HT) and low-temperature (LT) phases are composed of Mn II (S = 2 5 ) NC Fe III (S = 1 2 ) and Mn III (S = 2) NC Fe II (S = 0), respectively. A metal-to-metal charge transfer from Mn II to Fe III and a Jahn-Teller distortion of the produced Mn III ion cause this phenomenon. The magnetic transition entropy and enthalpy of the LT phase indicate that this phase shows a three-dimensional Heisenberg-type ferromagnetic lattice for the Mn III sites with a T c of 11.0 K, which is due to a valence delocalization mechanism. Ferromagnetic magnetization of LT phase in Rb 0.91 Mn 1.05 [Fe(CN) 6 ]โข0.6H 2 O is reduced by irradiation with only one-shot of laser pulse and the quantum yield is above one and reaches 4.5. This photomagnetic effect is caused by a photo-induced phase transition from the LT phase to the HT phase.