Abstract This study examined how cognitive aging affects emotional word processing using event-related potential technique. Young and older adults completed both implicit lexical decision and explicit emotion categorization tasks involving positive, negative, and neutral words. Behaviorally, older adults displayed a negative emotion effect in the implicit task, which was absent in young adults. While both age groups exhibited both positive and negative emotion effects in the explicit task, older adults demonstrated a greater positivity bias compared to young adults. Event-related potential technique data revealed that young adults exhibited an early negative emotion effect on the P2 and a late emotion effect on the late positivity potentials in the implicit task. In contrast, older adults exhibited an early negativity bias effect on the P2, as well as both negative and positive emotion effects on the N400, and positive emotion effects on the late positivity potentials. In the explicit task, young adults showed both early and late negative emotion effects on the P2 and late positivity potentials, while older adults showed both negative and positive emotion effects on the late positivity potentials. The results suggest distinct processing mechanisms for emotion words in young and older adults, involving both bottom–up and top–down mechanisms, which support the socioemotional selectivity theory.