The thermal conductivity of the antiferromagnet MnCl2·4H2O has been measured from 3° to 0.25°K with particular attention to the region of the Ne´el point (TN= 1.62°K). The effects of magnetic scattering are separated from the thermal resistance arising from nonmagnetic processes by comparing the thermal conductivity measured in a magnetic field of 40 kOe with that measured in zero applied field. It is found that in the paramagnetic phase there is no critically enhanced phonon scattering associated with the magnetic ordering transition. In the ordered phase the magnetic contribution to the scattering has a maximum near 0.75°K and diminishes as the transition is approached. Detailed comparison with theoretical predictions is made, and the relationship of this work to recent measurements of thermal expansion and specific heat is discussed.