A new pyridine-fused seleno-diazo-lium salt, 3-(phenyl-selan-yl)[1,2,4]selena-diazolo[4,5- a]pyridin-4-ylium chloride di-chloro-methane 0.352-solvate, C 12H 9N 2Se 2 +·Cl -·0.352CH 2Cl 2, was obtained from the reaction between 2-pyridyl-selenenyl chloride and phenyl-seleno-cyanate. Single-crystal structural analysis revealed the presence of C-H⋯N, C-H⋯Cl -, C-H⋯Se hydrogen bonds as well as chalcogen-chalcogen (Se⋯Se) and chalcogen-halogen (Se⋯Cl -) inter-actions. Non-covalent inter-actions were explored by DFT calculations followed by topological analysis of the electron density distribution (QTAIM analysis). The structure consists of pairs of seleno-diazo-lium moieties arranged in a head-to-tail fashion surrounding disordered di-chloro-methane mol-ecules. The assemblies are connected by C-H⋯Cl - and C-H⋯N hydrogen bonds, forming layers, which stack along the c-axis direction connected by bifurcated Se⋯Cl -⋯H-C inter-actions.