Neutron scattering has been used to measure the critical behaviour of the sublattice magnetization, M, and the gap in the spin wave energies at the Brillouin zone centre, E-0, for a single crystal of the quasi-2D antiferromagnet, MnPS3. The system was previously believed to be a good example of a Heisenberg-like antiferromagnet, however, the critical behaviour over most of the temperature range is more representative of an XY-like system. Just below the Neel temperature, there appears to be a cross-over to 3D critical behaviour. This signature is seen in the temperature dependences of both M and E-0. The nature of the anisotropy, which appears to be the final obstacle to a full understanding of the critical properties of MnPS3, is discussed. (c) 2006 Elsevier B.V. All rights reserved.