This meta-analysis synthesized 88 studies to investigate the processing advantages of emotion words over neutral words. Additionally, we explored the moderating effects of emotional properties (valence, arousal, emotion word type), linguistic factors (concreteness, frequency, length, neighborhood size), and task type in L1, advanced L2, and intermediate L2 speakers. We found a significant valence effect, with positive words showing a greater processing advantage than negative words only in L1 speakers. For arousal, the interaction analysis revealed that high arousal reduced the processing advantage of emotion words to a greater extent in intermediate L2 speakers than in L1 speakers. Furthermore, only advanced L2 speakers showed a significant processing advantage for emotion-label words compared to emotion-laden words. Regarding linguistic factors, longer word length was associated with greater processing advantages compared to shorter word length, but only in advanced L2 speakers. The greater processing advantage for concrete over abstract emotion words was observed only in intermediate L2 speakers, indicating that this group was the most sensitive to concreteness among all language speaker groups. Finally, task type significantly influenced emotion word processing in interaction with language proficiency. Overall, our findings support theoretical frameworks in both L1 and L2 processing and cognition.