Abstract: A cornice installation support system for supporting cornices of different widths at varying heights. The cornice installation support system includes a pair of support devices. Each support device comprises a tubular member, an extension arm and a support mount. The tubular member has a first end and a second end. An elongate extension arm extends the tubular member. The extension arm has a shape adapted to fit in the first end of the tubular member and has a first side with teeth thereon. A first and second bore is located in the tubular member. The first and second bores are diametrically opposed to each other. A gear extends the extension arm out of the tubular member. The gear has teeth thereon. A rod has the gear mounted thereon. The rod is rotatably mounted in the first and second bores, and the gear is intermeshed with the teeth on the extension arm. A mounting assembly receives the cornice. The mounting assembly has an L-shaped portion and is mounted to an end of the extension arm.