We study the effect of electron–phonon (e–ph) interaction on the coherent electronic conductance of a one-dimensional extended nanowire within the nearest-neighbour tight-binding and harmonic approximations. We suppose that the electrodes at the end of the wire are rigid and the e–ph interaction exists only in the centre of the wire. Therefore, we can use closed boundary conditions to diagonalize the phononic part of the centre wire Hamiltonian. After separating the phononic modes, we employ the Green's function technique for the electronic tight-binding Hamiltonian. Then, we calculate the electron transmission coefficient in the adiabatic regime at zero bias. The model is applied to a uniform chain and wires, which have alternating on-site or hopping energies. The results show that in all of these systems, the e–ph interaction has more effect on the conductance at the edges of the energy band. Additionally, in the systems including an internal gap, the effect of the e–ph interaction is negligible in the gap region, especially for long lengths of the centre wire.