The present study aimed to investigate the impact of social comparison on risk-taking behaviors and the neural underpinnings within a competitive context. Participants who thought they were playing against a stranger in a gambling task were actually playing against a programmed computer. Eighty-eight college students were assigned to one of three comparison conditions (downward, upward, and parallel) by varying the probability of gain. Behavioral results showed that disadvantage led to increased risk-taking. Event-related potential data analyses showed, in the parallel comparison condition, a significantly larger Feedback-Related Negativity (FRN) was induced by the self's safe decision than the risky decision and by loss rather than gain. However, in the upward and downward comparison conditions, larger FRN emerged solely in response to the loss of risky rather than safe decisions. On the P3 component, participants in the upward comparison condition showed no significant difference in response to their gain or loss, while the other two conditions did. The highest P3 amplitude, delta/theta power, and aperiodic activity were found in the closely matched condition. Finally, in the downward comparison condition, a stronger delta/theta power was correlated with a less risky decision. Overall, the findings indicate that parity heightens emotional arousal and engages more cognitive resources.