Although the polymer complex, poly(nickel 1,1,2,2-ethenetetrathiolate) (Ni-PETT), is an interesting n-type organic thermoelectric material, it is insoluble in all kinds of solvents. We prepared nanoparticles of Ni-PETT (n-Ni-PETTs) using a surfactant, dodecyltrimethylammonium bromide, as an additive during the synthesis of the polymer complex. The n-Ni-PETTs were well dispersed in an organic solvent like N-methyl-2-pyrrolidone, and could provide smooth, tough, and flexible n-type thermoelectric films by hybridization with poly(vinyl chloride).