Syntheses and infrared spectroscopic studies are reported for two different polymorphs of copper( I) thiocyanate and for adducts of copper(I) thiocyanate with thiourea (‘tu’) and ethylenethiourea (‘etu’ = imidazolidine-2-thione; (CH2NH)2CS)). These include the previously reported complex CuSCN/etu (1 : 2), which has a trigonal monomeric structure, and CuSCN/etu (1 : 1), which has a three-dimensional polymeric structure. A mechanochemical/infrared study of the CuSCN: tu (1 : 2) system showed that no 1 : 2 complex exists in this case, the product being a mixture of a 1 : 3 complex and a novel 1 : 0.5 complex. The latter complex was prepared both mechanochemically and from solution, and characterized by infrared and solid-state 65Cu broadline NMR spectroscopy. Diagnostic ligand and metal-ligand bands in the IR and far-IR spectra are assigned for both polymorphs of CuSCN and for all of the complexes studied and are discussed in relation to the structures of the complexes