Upon mixing an amidine dimer and 1,3,5-benzenetricarboxylic acid at the ratio of 3:2, a cylindrical complex was formed through multi-component self-assembly driven by amidinium-carboxylate salt bridge formation. The cylindrical structure of the complex was confirmed by 1H NMR and mass spectroscopies. The X-ray crystallographic analysis of the complex revealed that it had a cavity with a diameter of ca. 1 nm and adopted a triply-stranded helical structure in the solid state.