Dale Carnegie's best‐seller How to Win Friends & Influence People offers advice on leadership, interpersonal relationships, and persuasion. Though profoundly influential, Carnegie's self‐help book—including its nine guiding leadership principles—is based on anecdotes, case studies, and personal examples rather than empirical evidence. Examining the theoretical and empirical support behind Carnegie's leadership principles is essential for leaders to better understand whether to draw upon these principles and, if so, how and when to effectively use them in the workplace.