Open Source Software (OSS) is generally developed by interested professionals who have decided to participate in the process. The presence of effective leaders who both steer the development and motivate the developers is crucial to ensure a successful product. Using path-goal theory and built on leadership and motivation theories, we proposed and tested a model that can be used to assess the relationship between an OSS project leader’s leadership style and a developer’s motivation to contribute to the software development. We specifically decomposed the leadership and motivation construct to understand the hidden mechanisms by which leadership impacts motivation. A set of survey data collected from 118 OSS developers on Sourceforge.net was used to test our hypotheses. Our results indicate that leaders’ transformational leadership is positively related to developers’ intrinsic motivation and that leaders’ active management style is positively related to the developers’ extrinsic motivation.