We report measurements of the temperature dependence of the magnetic penetration depth lambda(T) in non-centrosymmetric superconductor Re_3W. We employed two experimental techniques: extraction of lambda(T) from magnetic {em dc}-susceptibility, measu
red on a powder sample, and the rf tunnel diode resonator technique, where a bulk polycrystalline sample was used. The results of both techniques agree: the temperature dependence of the penetration depth can be well described by weak-coupling, dirty-limit, s-wave BCS theory where we obtain $Delta(0)/k_BT_C=1.76$. No evidence for unconventional pairing resulting from the absence of the inversion symmetry is found.
