Two new examples of mixed metal copper(I) sulfites, namely, Na3Mn2Cu(SO3)4(H2O)5 (1) and NaMn4Cu(SO3)5(H2O)3 (2), have been synthesized and structurally characterized. The 1D structure of 1 is built from a chain of [Mn2Cu(SO3)4]3- bridged by Na+ ions whereas the structure of 2 features a complicated 3D framework in which Mn8O36 octanuclear clusters are bridged by sulfite anions and copper(I) ions into a 3D [CuMn4(SO3)5(H2O)3]2- network. The eight-coordinated sodium(I) ions are located at the cavities of the 3D structure. In both compounds, the oxygen atoms of the sulfite anion are bonded to Mn(II) ions whereas the sulfur atom is coordinated to the Cu+ ion. Magnetic measurements indicate that there exists antiferromagnetic interactions between Mn(II) centers in both compounds.