NASA’s Double Asteroid Redirection Test (DART) mission is the first planetary defense mission to directly test asteroid deflection by kinetic impactor. The DART mission will launch in summer 2021, and the impact in the 65803 Didymos binary asteroid system will occur in late September-early October 2022. DART will achieve a kinetic impact on the small asteroid “moonlet” Dimorphos by deliberately crashing the spacecraft into the moonlet to alter its orbit around the larger Didymos A. The effects of the impact will be assessed by measuring the change in the orbit period using telescopes on Earth. As part of the DART mission, simulations are being performed to better understand the expected results of the DART impact. Because the target properties and structure of Dimorphos are uncertain, it is important to simulate a variety of potential scenarios. Previous models showed that target structure (e.g., layering or porosity at the micro- and macro-scale) can significantly affect the cratering process and the expected momentum efficiency factor, β. Here, we report on results examining effects of target structure on the resultant deflection. We performed 57 2-dimensional CTH simulations of Dimorphos as a gravitational amalgamation of smaller rocks and regolith (to simulate an asteroid rubble pile). Each simulation included a random rubble configuration such that impact site structure varies across simulations. We catalogue crater morphology, amount of ejecta, and momentum transfer to the target for each simulation. We find that near-surface target structure (e.g., whether the impact site is in regolith or on a boulder) affects the crater size and shape, but does not generally have significant effects on the momentum enhancement. The choice of material plasticity models shows a larger effect than randomized surface structure. In some cases, however, local boulder fields can have a large effect if boulders are ejected.