The effect of fiber end geometry, especially one with an enlarged spherical end, on the stress distribution in a polycarbonate/short glass-fiber reinforced model composite was studied using photoelasticity and finite element analysis (FEA). The role played by the fiber/matrix interfacial strength was also investigated. The photoelastic method was applied to examine the stress distribution in the vicinity of a single fiber embedded in a thermoplastic polycarbonate matrix. Linear elastic, axisymmetric FEA was carried out to investigate the fibers effectiveness as a load bearing constituent, the effect of interfacial debonding, and stress concentration near the fiber ends. Both photoelastic analysis and FEA demonstrated the efficiency of the spherical enlarged fiber end in load transfer ability and in delayed debonding, which may be important in enhancing strength and modulus of thermoplastic matrices.