A joint assembly of vapor chambers connects the vapor chambers to effectuate joint operation thereof. For example, two paired vapor chambers are connected therebetween by a capillary pipe and a gas pipe. The capillary pipe is filled with a third wick which connects with a first wick and a second wick in the two vapor chambers. The two vapor chambers are in spatial communication with each other because of the gas pipe. A working fluid in the two vapor chambers is transferred between the first, second and third wicks by capillarity. The gas-phase working fluid moves between the two vapor chambers via the gas pipe, thereby allowing the two vapor chambers to operate jointly.