Machiavellians are said to be manipulative people who reduce the social capital of the organization. Yet some authors note that Machiavellians are also highly adaptive individuals who are able to contribute, cooperate, and use pro-social strategies when it is advantageous to them. Here we study whether transformational leader behavior can stimulate Machiavellian followers to engage in organizationally desirable behaviors such as challenging organizational citizenship behavior. We hypothesized and found in two multi-source field studies that transformational leadership moderates the relationship between Machiavellianism and challenging organizational citizenship behavior. In Study 2, we hypothesized a moderated mediation model and found that enhanced job autonomy and accompanying intrinsic motivation relating to transformational leadership explain (part of) the relationship between transformational leader behavior and challenging citizenship behavior of Machiavellian followers.