<p>This study presents the design and evaluation of a customized ankle–foot orthosis (AFO) using a combined approach of photogrammetry, CAD modeling, numerical analysis, experimental validation, and 3D printing. The orthosis was developed for a 10-year-old female participant (weight 55 kg) who was recovering from a right ankle sprain. The shape of the participant’s foot was captured using a photogrammetry technique, which is a simple and low-cost method to create a 3D model from multiple images. The obtained foot model was used in CAD software to design an orthosis that closely matches the actual shape of the participant’s foot. Three different designs (DS-1, DS-2, and DS-3) were developed by changing the thickness and adding reinforcement. Finite element analysis was carried out to study stress distribution and deformation under walking conditions such as mid-stance and terminal stance. To consider the effect of printing direction, the material (PLA) was tested experimentally using tensile, compressive, and shear tests. Based on these results, the Tsai–Wu failure criterion was used to check the safety of the design. Among all designs, DS-3 showed the lowest stress values and highest safety factor, and its failure index was well below the critical limit. The novelty of this work is the integration of low-cost photogrammetry, CAD modeling, anisotropic FEM analysis, and experimental validation to design and develop a participant-specific ankle–foot orthosis using 3D printing.</p>