The crystal structure of the title compound, poly[bis-(tri-methyl-ammonium) hexa-μ(1,1)-azido-tetra-azido-tricobalt-ate(II,III)], [(CH(3))(3)NH](2)[Co(II)Co(III) (2)(N(3))(10)], consists of anionic chains [Co(II)Co(III) (2)(N(3))(10)](2-) extending parallel to the c axis and [(CH(3))(3)NH](+) counter-cations situated between the chains. In the anionic chain, one tetra-hedrally coordinated Co(II) atom (site symmetry 2) and two octa-hedrally coordinated Co(III) atoms are arranged alternately and are linked by μ(1,1)-azide bridges. The anionic chains and cations are connected via N-H⋯N hydrogen bonding into a three-dimensional structure.