Cartilage repair remains a significant clinical challenge due to the tissue’s limited self-healing capacity, avascular structure, and complex mechanical requirements. Recent advances in additive manufacturing have enabled the fabrication of patient-specific scaffolds with controlled architecture and tunable mechanical properties. Among high-performance biomaterials, polyether ether ketone (PEEK) has emerged as a promising matrix material owing to its excellent chemical stability, thermal resistance, and mechanical strength. However, pristine PEEK is bioinert and hydrophobic, limiting its biological performance in cartilage regeneration. To address this limitation, fiber reinforcement and bioactive filler incorporation have been widely investigated to enhance both mechanical and biological functionality. This study provides a comparative analysis of different fiber types incorporated into 3D-printed PEEK composites for cartilage repair, considering fiber composition (carbon, glass, ceramic, natural, and polymeric), size (Nano to micro-scale), length (short, long, continuous, discontinuous), morphology, and volume fraction. The influence of fiber characteristics on mechanical performance—including tensile strength, compressive modulus, fatigue resistance, and interfacial bonding—as well as biological responses such as cell adhesion, proliferation, and extracellular matrix formation, is critically evaluated. Furthermore, the interaction between fiber selection and 3D printing parameters, including build orientation, infill density, layer thickness, and extrusion temperature, discussed. Comparative findings suggest that hybrid reinforcement systems, particularly short carbon fibers combined with bioactive Nano-fillers such as Nano-hydroxyapatite or graphene oxide, offer an optimal balance between mechanical integrity and bioactivity. Continuous carbon fibers provide superior strength but limited biological enhancement, whereas Nano-scale bioactive reinforcements improve cellular responses with moderate mechanical gains. Strategic optimization of fiber type, geometry, and processing conditions is essential to achieve mechanically robust and biologically functional 3D-printed PEEK scaffolds for cartilage regeneration.