The electric quadrupole coupling constant eqQ/h of Na-25 (I-pi = 5/2(+), T-1/2 = 59.6 s), implanted in a TiO2 single crystal, has been measured by use of the beta-NMR technique, to determine the electric quadrupole moment Q. As a result, vertical bar eqQ/h vertical bar = (44 +/- 16) kHz and vertical bar Q(Na-25)vertical bar = (1.0 +/- 0.4) mb were determined. From the NMR on 25Na in NaCl, the magnetic moment was determined as vertical bar mu vertical bar = (3.6832 +/- 0.0003) mu(N).