Abstract: Crane swing warning system is disclosed for a crane that has an undercarriage, which is independent from its cab body, connected by a turntable that the upper crane body rotates about on a vertical axis. The crane swing warning system consists of a continuous plastic caution tape extended out and around the upper crane body by supports adjustable in 360 degrees, and in length, fully retractable or completely removed. This crane swing warning system is to warn individuals of the movement of the upper crane body as to prevent the individuals from being struck by or being caught between the rotating upper crane body and the crane undercarriage.