<p>Z-pin reinforcement technology has been demonstrated to significantly enhance the interlaminar mechanical properties of composite materials. The reinforcement effect is influenced by several factors, including laminate architecture, mode mixity, and z-pin characteristics. This study investigates the effect of z-pin elastic modulus on the mode-II delamination behavior of composite laminates. Two types of z-pin-reinforced laminates were designed and fabricated, while unpinned laminates were used as control specimens. Mode-II delamination tests were performed using a 4ENF configuration. The results show that z-pinning markedly increases both the ultimate load and the fracture toughness of the laminates. An experimental mode-II <i>R</i>-curve was obtained, and the associated failure mechanisms were analyzed. The steady-state fracture toughness was higher for carbon fiber z-pinned specimens than for polyimide fiber z-pinned ones. Numerical simulations of the delamination were conducted by integrating a cohesive zone model with a bilinear constitutive law and a shear model implemented via nonlinear spring elements. The close agreement between simulated and experimental load–displacement curves confirms the accuracy of the numerical model. This work provides valuable theoretical insight and technical support for the application of z-pin reinforcement technology in advanced composite structures.</p>