In this study, water swelling coefficients and activation energies for eucalyptus and poplar woods were calculated. The swelling properties of both species appear to directly proportional dependence on temperature and its directions. In the tangential direction, the swelling rate coefficients of eucalyptus ranged from 0.30 to 0.69 are greater than that of poplar which ranged from 0.24 to 0.55. In comparison to average activation energy (Ea), poplar approximately have 2.6 kJ/mole higher Ea than eucalyptus (36.7 vs 39.3 kJ/mole). The comparison and the measured results reveal that the swelling response of both woods with temperature can be quite well predicted using Arrhenius kinetic theory.