A feedthrough filter capacitor assembly (10) and related installation method are provided for shielding a conductive terminal pin or lead (12) of the type used, for example, in an implantable medical device such as a heart pacemaker or defibrillator, against passage of external interference signals. The feedthrough assembly (10) includes a terminal pin subassembly (26) having at least one terminal pin (12) supported within a cylindrical conductive ferrule (28) by a hermetically sealed insulator ring (30). The ferrule (28) is adapted for mounting onto a conductive pacemaker housing (22), as by welding or brazing, to support the terminal pin (12) for feedthrough passage to the housing interior. A co-axial filter capacitor (24) is mounted at an inboard side of the pacemaker housing (22), with capacitor electrode plate sets (40,42) coupled respectively to the pacemaker housing (22) and to the terminal pin (12) by a conductive adhesive (54) or the like. In one preferred form, multiple filter capacitors are provided in a substantially coplanar array within a common base structure, with each capacitor in association with a respective terminal pin.