The aggregation chemistry of thionyl chloride has been studied in organic solvents including dimethyl sulfoxide, N,N’-dimethylformamide, and propylene carbonate employing ultraviolet (UV) absorption spectroscopic and cyclic voltammetric experiments. Results indicate that thionyl chloride undergoes a self-association equilibrium at high concentrations in these solvents. Equilibrium constants of dimerization reactions in these solvents and molar absorptivities of dimers at their absorption maxima are reported. At higher concentrations, aggregates of more than three thionyl chloride molecules are observed.