An injection molded foam bicycle helmet is disclosed and is constructed from a dome-shaped internal frame and a surrounding coating of a foam based material. The dome-shaped frame is formed from an integrally molded, planar member including an annular lower perimeter body, at least one lateral arc-shaped rib extending from one side of the body to the opposite side of the body, and at least one longitudinal arc-shaped rib extending from the front of the body to the rear of the body. Both the lateral and longitudinal ribs deform out of the plane of the body and into arched configurations, thereby forming the dome-shaped frame. Each lateral rib is also operative to engage each of the longitudinal ribs so as to provide additional structural support for the frame. A number of positioning pins are also formed along the inwardly and outwardly facing sides of the body and the ribs for centrally positioning the frame within the mold.