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Stresses required to debond the fiber-matrix interface and to pull out a fiber are analyzed as a function of the embedded fiber length for a fiber-reinforced composite. The role of residual clamping stresses at the interface is considered. During fiber pull-out, Poisson contraction of the fiber in the radial direction reduces the resultant compressive stress at the interface and, hence, the interfacial frictional stress. This leads to a non-linear dependence of both the stress required for complete interfacial debonding and the stress for fiber pull-out on the embedded fiber length. Excellent agreement between present theoretical analyses and existing experimental results is obtained. Compared with the stress required for fiber pushout, where the fiber is subjected to compression in its axial direction, the stress required for fiber pullout is lower owing to Poisson's effect.