A copper manganese hydroxide oxide, CuMn2.22O5.25.2.04H(2)O, which has a novel misfit-layered structure built with pseudohexagonal MnO2 and orthorhombic Cu(OH)(2) sheets, has been hydrothermally synthesized by using the layered birnessite as the precursor. This compound has been investigated by XRD, SEM, TEM, SAED, and TG-DTA. In this compound, manganese oxide sublattice is hexagonal with a(1) = 0.282 and c(1) = 0.942 nm, and copper hydroxide sublattice is orthorhombic and has a C-center with a(2) = 0.578, b(2) = 0.276, and c(2) = 0.942 nm. The two sublattices in this compound have different symmetry, and they are incommensurate along a direction in ab plane.