This study presents the development of automatic hydraulic butt fusion welding machine to weld dissimilar plastic pipes together. The designed and fabricated welding machine can be used to weld the butt-fused joints of similar and dissimilar plastic pipes. This welding machine has two heating plates that permit heating the two plastic pipe ends at different temperatures depending on the welding temperature of each plastic pipe material. To create different pressure at two pipe ends as well as to bring the pipe ends into heating at different times, this welding machine uses four hydraulic cylinders. Each pair of jaws at one side is mounted on two movable cylinders which create the forward and backward movement of a pipe during welding. The welding machine is controlled automatically via the programmable logic controller and the human machine interface screen.