Embodiments of heat spreaders with integrated preforms, and related devices and methods, are disclosed herein. In some embodiments, a heat spreader may include: a frame formed of a metal material, wherein the metal material is a zinc alloy or an aluminum alloy; a preform secured in the frame, wherein the preform has a thermal conductivity higher than a thermal conductivity of the metal material; and a recess having at least one sidewall formed by the frame. The metal material may have an equiaxed grain structure. In some embodiments, the equiaxed grain structure may be formed by squeeze-casting or rheocasting the metal material.