According to a longstanding consensus among researchers, individual differences play a limited role in predicting negotiation outcomes. This consensus stemmed from an early narrative review based on limited data. Testing the validity of this consensus, a meta-analysis of negotiation studies revealed a significant role for a wide range of individual difference variables. Cognitive ability, emotional intelligence, and numerous personality traits demonstrated predictive validity over multiple outcome measures. Relevant criteria included individual economic value, joint economic value, and psychological subjective value for both the negotiator and counterpart. Each of the Big 5 personality traits predicted at least one outcome measure, with the exception of conscientiousness. Characteristics of research design moderated some associations. Field data showed stronger effects than did laboratory studies. The authors conclude that the irrelevance consensus was misguided, and consider implications for theory, education, and practice.