The paper presents the solution of the problem of bending of a large aspect ratio simply supported sandwich panel with cross-ply facings subject to an elevated temperature or heat flux on one of the surfaces. The geometrically and physically linear problem for the central section is solved exactly in the cases where long edges are either unrestrained against or completely prevented from axial displacements. Wrinkling of the facings is also investigated, accounting for both thermal stresses as well as the effect of temperature on the properties of the facings and core. It is shown that thermally induced wrinkling may become the dominant mode of failure in a panel that does not wrinkle at the room temperature.