The current study investigated the effects of easy versus difficult math on event-related potentials as a function of self-esteem in 28 undergraduate students. First, it was found that participants responded much more rapidly to an easy task. Second, the amplitude of P2 (150–300 ms) was more positive amplified in low self-esteem participants when compared to high self-esteem participants. Third, the difficult task elicited a greater N2 (300–450 ms) component than the easy task, but only in the low self-esteem participants. Finally, the easy task elicited a greater late positive component (LPC: 450–600 ms) compared with the difficult task and the difficult task elicited a greater LPC (900–1200 ms) components compared with the easy task separately, which were consistent with behavioral reaction times. We speculate that the difficult math might have induced more negative emotions in subjects with low self-esteem, and that low self-esteem individuals might be more susceptible to interpret the difficult task as threatening.