Breath-focused mindfulness (BFM), which induces changes in brain structure and function, is applied in the clinical treatment of mental disorders as a method to regulate one's emotions. However, whether BFM works through a top-down emotional regulation strategy to alter brain dynamics and its relationship with individual differences in trait mindfulness are unclear. Event-related potentials (ERPs) of 20 healthy BFM-naive undergraduates were recorded when they conducted BFM/viewing tasks while viewing affective pictures. Participants completed the Attentional Control Scale (ACS) and the Mindful Attention Awareness Scale (MAAS). The results indicated that under the viewing condition, positive and negative pictures elicited greater P1, N2, and late positive potential (LPP) amplitudes than did neutral pictures. However, BFM attenuated P1, N2, and LPP amplitudes for positive and negative pictures but not for neutral pictures. P1 amplitudes for emotional minus neutral pictures correlated with individual differences in focus attention measured by the ACS, while N2 amplitudes for emotional minus neutral pictures correlated with individual differences in trait mindfulness measured by the MAAS. These observations suggest that, consistent with the dual-process model, BFM is an effective emotion regulation strategy and might activate the dorsal top-down prefrontal system to alter early and late neural dynamics of affective processing.