Development of a rehabilitation harness to aid in recovery from musculoskeletal injuries is needed because serious complications can arise from long-term use of rescue slings. This study’s objective was to determine the anatomical structures of the horse that can bear significant weight, the potential complications that could arise if a horse is not properly supported by the harness and the % weight compensation achievable with the newly developed harness when used together with a dynamic rehabilitation lift. This dynamic lift can reduce the load the limbs carry, either withers-to-pelvis or left-to-right when used in combination with the rehabilitation harness under development. The rehabilitation harness prototype described here was made of cotton/nylon with sheepskin inserts, forming a blanket with high-strength strapping supporting the load-bearing structures of the horse. This prototype was load tested up to 600 kg, for safety, with no sign of failure. In an adult horse, the harness allowed for 40% load reduction from both front (125 of 303 kg [60% of 506 kg]) and hind (80 of 203 kg [40% of 506 kg]) legs before complications (abnormal posture) occurred. Pressure was measured to determine areas of high pressure which lead to the addition of an H-frame and a figure-eight pattern of strapping to the forelimb support reducing pressure, improving posture and achieving greater load reduction (46% [140 of 301.2 kg]). Abnormalities in respiratory rate or pattern were not observed. Future research will include testing the harness longer term (up to six weeks) with the incorporation of an air-pressurised breastplate to detect high-pressure, high-temperature, high-moisture areas, modifying the design further for improved horse-comfort reducing the risk of complications and enabling long-term use of the harness during rehabilitation.