We advance the trait approach to leadership by leveraging a large multinational database on leader emergence (k = 120 samples, N = 32,579) and leader effectiveness (k = 116, N = 42,487) to extend Judge et al.'s (2002) classic meta-analysis of Big Five personality and leadership. By testing novel hypotheses rooted in culturally endorsed implicit leadership theory and socioanalytic theory, we offer three unique insights. First, in collectivist societies (cultures that value interdependence with one's group), the five factor model traits-and leader Extraversion and Agreeableness in particular-are stronger predictors of leader effectiveness, consistent with the theorized need for enhanced social coordination in such cultures. Second, a theoretical model is proposed to specify that leader Big Five trait effects are mediated by leader behavior (confirming that Consideration mediates Extraversion and Agreeableness, whereas Initiating Structure mediates Conscientiousness, Extraversion, and Openness). Third, trait Honesty-Humility robustly predicts leader effectiveness beyond the Big Five traits, expanding the trait approach. New implications for understanding when and why personality traits predict leadership are discussed. (PsycInfo Database Record (c) 2024 APA, all rights reserved).