Recent work has supported the role of reasoning in third-party moral judgment of harm transgressions. In particular, reasoning may increase the weight of intention in moral judgment, especially following accidental harm, a situation that presumably requires judges to balance considerations about the outcome endured by a victim on the one hand and considerations about an agent's intention to cause harm on the other hand. Three preregistered lab-based studies aimed to test the causal contribution of reasoning to moral judgment of harm transgressions using experimental manipulations borrowed from the reasoning literature: time pressure (Experiment 1), cognitive load (Experiment 2), and priming (Experiment 3). Participants (N = 284) were presented with short fictitious scenarios in which the agent's intention toward a potential victim (harmful or neutral intent) and the action's outcome (victim's injury or no harm) were manipulated. Participants then reported their moral judgment of the agent's behavior (wrongness and deserved punishment) and their empathy toward the victim. We found that time pressure reduced judgment severity toward agents who had the intention to harm, but the reasoning manipulations overall did not impact judgment severity toward agents who harmed accidentally. We discuss why reasoning may sometimes influence how individuals account for intention in third-party moral judgment of harm transgressions.