Abstract: A convertible dolly cart system which may convert between a traditional floor dolly and a sheet goods cart in a quick and efficient manner. The convertible dolly cart system generally includes a flat, rectangular cart having a central opening and a panel support insert which is removably positioned within the central opening of the cart for use in transporting large sheets of material such as sheetrock or wall panels. The panel support insert includes a base on which the sheets of material may be placed and an upper support assembly against which the sheets of material may be rested. Thus, the present invention is easily convertible between a dolly cart and a sheet goods cart.