The present disclosure provides leadless pacemaker systems and methods. A leadless pacemaker includes a battery subassembly, a feedthrough subassembly, and an electronics subassembly coupled between the battery subassembly and the feedthrough subassembly, the electronics subassembly including an electronics package, and a housing configured to provide a hermetic seal and comprising a first retaining feature and a second retaining feature configured to secure the electronics package within the housing.