We introduced a novel technique to fabricate a Microlattice-cored miniature sandwich panel with an ultralow density. This sandwich panel was made of a monolithic Ni-P foil without any bonding between the core and the faces. As a preliminary study, the mechanical properties were evaluated under compression in two different loading directions, and the effects of the face sheets added on the top and bottom were investigated in comparison to the conventional Microlattice without the face sheets. Under the out-of-plane compression, almost no difference was evident between the conventional Microlattice and the Microlattice sandwich in their compressive behaviors, because of the high friction with the compression platens. However, under the in-plane compression, the addition of the face sheets to the conventional Microlattice significantly increased the strength and stiffness, when the wall thickness was higher than a certain limit. Otherwise, the reinforcing effect became much less significant, because the very thin face sheets were easily buckled across the entire area even at the beginning of the loading.