Purpose-The purpose of this paper is to evaluate the influence of psychological hardiness, social judgment, and "Big Five" personality dimensions on leader performance in US military academy cadets at West Point. Design/methodology/approach-Army cadets were studied in two different organizational contexts, i.e. summer field training and during academic semesters. Leader performance was measured with leadership grades (supervisor ratings) aggregated over four years at West Point. Findings-After controlling for general intellectual abilities, hierarchical regression results showed leader performance in the summer field training environment is predicted by Big Five extroversion, and hardiness, and a trend for social judgment. During the academic period context, leader performance is predicted by mental abilities, Big Five conscientiousness, and hardiness, with a trend for social judgment. Research limitations/implications-Results confirm the importance of psychological hardiness, extroversion, and conscientiousness as factors influencing leader effectiveness, and suggest that social judgment aspects of emotional intelligence can also be important. These results also show that different Big Five personality factors may influence leadership in different organizational contexts. Practical implications-The study identifies personality factors related to leader performance in different types of work environments or contexts. Results can be used to improve leader selection and development programs. Originality/value-This is the first study to examine the influence of psychological hardiness together with Big Five personality factors on leader performance. It identifies hardiness as an important predictor of leadership, while also showing that organizational context makes a difference for what Big Five personality factors influence leader performance: extroversion appears to be more influential in highly social and active work environments, whereas conscientiousness has greater salience in academic and business settings.