Neutron powder diffraction shows that the intermetallic Er(2)Fe(17) compound with hexagonal crystal structure has a ferrimagnetic ground state (T(C) = 303 K). At T = 5 K the magnetic moments of Fe sublattice (mu similar to 2 mu(B)) are therefore antiparalell to those of the Er one (mu similar to 9 mu(B)), all of them lying on the basal plane. This compound exhibits strong magneto-volume effects up to temperatures in the vicinity of T(C). Neutron thermo-diffraction experiments also show an anomalous temperature dependence of the cell volume, including a negative thermal expansion coefficient below 300 K. In addition, a positive spontaneous volume magnetostriction is observed up to T similar to 400 K, with a maximum (omega(S) similar to 0.02) located at T = 5 K.