Interpersonal curiosity (IPC) is an important intrinsic motivation in social interaction, yet studies focused on its neural mechanism are rare. In a three-agent (Self, Other, or Computer) interactive gambling task, we recorded event-related potentials (ERPs) to a cue stimuli indicating whether participants will be informed of their own, of another participant's or the computer's outcomes such that curiosity will be satisfied (CWS) or curiosity will not be satisfied (CWN). The results showed that relative to the CWS cue stimuli the CWN cue evoked a larger late positive component (LPC) between approximately 400 ms and 700 ms after cue onset in both the Self and Other conditions, but not in the Computer condition. Additionally, participants reported stronger curiosity in the Other's outcomes than in the Computer's outcomes. Most importantly, participants’ subjective rating of curiosity was significantly correlated with the amplitude of the LPC elicited by the CWN cue. Furthermore, scores in the “curiosity about emotion” subscale of the IPC Scale was significantly correlated with the LPC amplitude when the participants learn they will not be informed of the Other's outcomes. We suggest that (1) interpersonal information is of great significance to individuals and IPC is an important social motivator, and (2) LPC amplitude is sensitive toIPC.