A harness system for adjusting support of a garment is provided herein. The garment with a harness system includes a body and a liner having harness straps. The harness straps slide through openings in shoulder straps of the body. The harness straps are then laced through a series of maintainers in the back of the body. The harness straps having terminally-located tabs that may be pulled from the back of the body toward the front of the body and affixed thereto. The placement of the tabs, when pulled toward the front of the body and attached thereto, determines the fit and support of the garment. By manipulating the tabs of the harness system, a wearer may adjust the length of the harness straps, back and posture support, and the lift provided by the liner. The harness system creates a customizable fit and support level.