In this paper, a simple solution route was developed for the controllable synthesis of coordination polymer Mn₂Mo(CN)₈·xH₂O micro/nano-crystals with unique and multiform morphologies. The syntheses involve the precipitation of Mn²⁺ and Mo(CN)₈⁴⁻ in aqueous solution with polyvinylpyrrolidone (PVP) as a capping agent. By simply tuning the experimental parameters such as reaction temperature, concentration of raw materials, feed ratio of Mn²⁺ to PVP, and the anions used, Mn₂Mo(CN)₈·xH₂O micro/nano-crystals with various interesting morphologies including square plate-like, rice-like, flower-like, rod-like, octahedron, and hollow-core square plate structures were successfully obtained. The possible formation mechanism for these Mn₂Mo(CN)₈·xH₂O micro/nano-crystals was also proposed. It is expected that this morphology-controlled crystal growth can be extended to the synthesis of micro/nano-structures of a wide range of coordination polymer materials with various functions.