Stark effect measurements have been performed on three rotational transitions of the H2SO4-H2O complex using pulsed-nozzle Fourier transform microwave spectroscopy. The total dipole moment (μT), as well as its projection onto the a-inertial axis of the complex (μa), have been determined for each of two tunneling states, designated A and B. For the A state, μT is 3.024(94) D and μa is 2.630(20) D. For the B state, these values are 3.052(17) and 2.6402(65) D, respectively. Ab initio calculations at the HF/aug-cc-pVTZ, MP2/aug-cc-pVDZ, MP2/ aug-cc-pVTZ, MP2/aug-cc-pVQZ, and MP3/aug-cc-pVDZ level/basis set have been performed and compared with experimental values for both H2SO4 and H2SO4-H2O. Models for homogeneous nucleation requiring the dipole moment of the H2SO4-H2O adduct should use the B-state value of μT = 3.052(17) D.