Human decisions are often made in a social context, thereby relying on the ability to anticipate and predict others’ behavior. In such contexts, gaze is an important communicative signal which can inform individuals about others’ intentions, goals and upcoming decisions. Gaze has been shown to affect various cognitive processes and states in human interactions. Nevertheless, the effect of gaze on social decision-making is still understudied. Here, we investigated the effect of mutual gaze exhibited by a humanoid agent in an interactive setup. Participants (N=40) played a strategic game against the robot iCub while we measured their behavior and neural (EEG) activity. Critically, participants were instructed to look at the robot before choosing their next move. During that time period, we manipulated the iCub's behavior to either establish eye contact (mutual gaze) or avoid eye contact (averted gaze) with them. This manipulation was orthogonal to the robot’s choices. Participants were assigned either to a group with 70% instances of mutual gaze or 70% of instances of averted gaze. As a result, participants were slower to respond in the mutual gaze condition, relative to averted gaze. Based on the drift diffusion model, we found that this delay was driven by an increase of the decision threshold. This behavioral effect was paralleled by higher alpha synchronization during mutual gaze, suggesting a stronger need to suppress the distracting gaze signal. Overall, our results indicate that mutual gaze engages brain resources for managing social signals. Even when this social signal is irrelevant to the decisions to be made, its processing can influence decision time, neural synchronization, choice strategies and sensitivity to outcomes. These findings underline how communicative behaviors can be impactful in real-world decision-making.