The quadrupole coupling tensor of95Mo in mesitylene-d1, molybdenum tricarbonyl is determined in benzene solution by NMR of the dielectrically aligned molecule. The largest principal component e2qQ/h, which lies along the dipole moment of the complex, is ±(954 ± 50) kHz. The asymmetry parameter η is zero because of symmetry considerations. A value of 10-9 ± 0-6 MHz for the quadrupole coupling constant of97Mo is obtained by evaluating the quadrupole-moment ratio of97Mo and95Mo. Rotational diffusion of the complex in solution is investigated by relaxation measurements. The dipole moment of the complex is estimated to be (2.1 ± 0.1) x 10-29Cm (6-2 +0-4 D).