The addition of Z-yarns to an S-2 glass composite can increase the material's resistance to interlayer delamination and damage. However, the presence of the Z-yarns also complicates the resulting constitutive behavior, as multiple individual failure mechanisms (e.g. yarn/matrix delamination, yarn breakage) may occur before the overall ultimate failure of the composite is reached. A mesoscale model of a 3D-weave composite was created to provide insights into these processes. Material models for the yarns, matrix, and interfaces were previously developed for a similar plain-weave composite. These were combined with a complicated unit cell geometry that could be used to construct specimen meshes that closely matched the physical characteristics of the 3D-weave composite. Numerical simulations conducted using this model can reproduce most aspects of the load–displacement curves and the observed failure mechanisms from tension, torsion, and delamination tests.