Continuous drive friction welding (CDFW) is a solid-state joining procedure that can be used to join various similar and dissimilar materials. High-density polyethylene (HDPE) is a thermoplastic that can replace many traditional materials. Utilizing experimental design procedures such as response surface method (RSM) is a reliable approach for determining the most significant process parameters and optimizing the desired responses. The current study employed an RSM experimental design to investigate the effects of the process parameters for welding HDPE rods using CDFW. The design evaluated the process parameters and three outcome responses: the maximum welding temperature, the axial shortening, and the tensile strength (TS). The combination of the three responses can allow achieving high-efficiency welds. The results showed that it was possible to achieve high-efficiency welds while maintaining axial shortening and controlling temperature. A TS >65% of the parent material's strength with an axial shortening of <3 mm was achieved.