Abstract Dielectrophoresis (DEP) technique was used to assemble carbon nanotubes (CNTs) arrays and CNTs networks between parallel electrodes with different gap sizes. Carboxylic-functionalized CNTs were prepared to carry out DEP experiment in terms of their good dispersion in N , N -dimethylformamide (DMF) without using any surfactants. From the characterization of assembled structures and numerical simulations of the electric field, it is found that the dielectrophoretic nanotube–nanotube interactions play crucial roles in DEP assembly. The obtained results show that the dielectrophoretic force fields and the DEP interactions among CNTs vary with the length of CNTs relative to the size of the electrode gap, leading to the variation of self-assembled structures. The results can help analyze the assembly of CNTs between the parallel electrodes.