A modular implantable medical device permits implantable medical devices to have a smaller profile in order to better fit into locations within the human body. A modular implantable medical device separates various functional components of the implantable medical device into a set of interconnected modules. This distributed architecture of a modular implantable medical device may permit the device footprint to be distributed over a larger area while making the profile smaller, and may permit the overall shape of the implantable medical device to better match the body location into which it is to be implanted. An overmold integrates the modules of a modular implantable medical device into a single structure. In some embodiments the overmold is flexible and provides a biocompatible interface from the component modules and the patient, while restraining potentially harmful intermodule motion.