Immersive virtual reality (VR) allows us to achieve very high levels of fidelity. This study evaluated display fidelity and interaction fidelity independently, at extremely high and low levels, for a VR first-person shooter (FPS) game. The goal was to gain a better understanding of the effects of fidelity on the user in a complex, performance-intensive context. The results of the study indicate that both display and interaction fidelity significantly affect strategy and performance, as well as subjective judgments of presence, engagement, and usability. In particular, performance results were strongly in favor of two conditions: low-display, low-interaction fidelity (representative of traditional FPS games) and high-display, high-interaction fidelity (similar to the real world).