Orthotics are worn to assist neuromuscular and skeletal systems. These devices are used in gait rehabilitation programs for patients who sustained a brain injury or lower leg trauma. An orthotics’ effectiveness in gait rehabilitation depends upon the fit to the user and comfort in wearing it. In this paper, we present an automated design of a composite leg calf shank component of an actively controlled orthotic device. The shank has a complex combination of geometric, stiffness, strength, and manufacturing constraints. Additively manufactured composites provide lightweight designs that meet mechanical performance and low-cost manufacturing requirements. To this end, we created an automated and patient-customized orthotic design that begins with a scan of the patient’s leg and produces a design for a 3D-printed short carbon fiber-reinforced or a continuous carbon fiber composite calf shank. The design, analysis, and testing pipeline for a patient-customized 3D-printed short-fiber composite shank is described.