This research focuses on modeling the microstructure of aluminum and simulating the initiation of fatigue cracks along grain boundaries using a cohesive zone model. Initial observations about the use of the cohesive zone model and the grain boundary response were made using simulations of bicrystals and small regular polycrystals under simple tension loading. Next, statistically generated polycrystal samples were created and loaded, resulting in crack initiation along the grain boundaries. How simulations were conducted, and observations from the simulations of the initiation sights and propagation of decohesion are discussed. The simulation tool created to use cohesive zone models and statistical representations of polycrystals combine to predict fatigue crack initiation.