Over-molded IC package assemblies including an in-mold capacitor. In some embodiments, an over-molded package assembly includes a IC chip or die coupled to one or more metal distribution layer or package substrate. A molding compound encapsulates at least the IC chip and one or more capacitors are fabricated within the molding compound. The capacitors may include two or more metal plates separated by an intervening dielectric material, all of which are embedded within a trench in the molding compound. Individual ones of the capacitor plates may physically contact a conductive land of the package redistribution layer or package substrate, for example to tie the plates to a ground plane and power plane, or two supply rails, in a decoupling capacitor application.