A one-piece inner garnish assembly module system (MS) joins an inner garnish molding (IG), primary seal (PS), glass run (GR), and inner beltline weatherstrip (IB) into a single component prior to installation of the module system on a vehicle. The garnish is secured to the glass run along the A and B pillars, and the interconnecting header portion of a vehicle door. In addition, the primary seal is operatively associated or secured to the garnish, and may be pin-mounted to the door, or mechanically connected, and/or adhesively secured to the door.