The relationship between grit and transformational leadership behavior was investigated, using both self‐reported behavior and behavioral ratings by followers, peers, and managers. A multi‐source sample of surveys from leaders (6,654) and their associates (47,159) from thousands of organizations in 78 countries and 22 industries was analyzed using mixed‐effect multilevel models. Grit predicted both self‐reported and observer‐reported transformational leadership behavior. The relationships were complex, with each component of grit (i.e., perseverance and consistency) having statistically significant but different behavioral associations both within and between raters. The findings reveal the potential for grit to predict transformational leadership behavior, highlighting the theoretical and practical implications of the trait of grit when identifying, developing, and supporting leaders.