The strain hardening behavior of Al-TiN nanolayered composites induced by plastic incompatibility was studied by 3-D discrete dislocation dynamics (DDD) simulations. Our simulations results indicate the strain hardening rate solely induced by the plastic incompatibility is independent of layer thickness and dislocation density at a constant layer thickness ratio, while the yield stress exhibits a strong size effect. Furthermore, the strain hardening rate increases with decreasing Al/TiN layer thickness ratio and our predicted results match well with prior experiment data.