The Dualistic Model of Passion (Vallerand et al., 2003) shows that people can experience a harmonious or an obsessive passion toward an activity. Mageau and Vallerand (2007; Mageau et al., 2009) have argued that self-related processes, such as contingencies of self-worth, are central in the distinction between the two types of passion. Specifically, it was proposed that people with an obsessive passion rely more heavily on their passionate activity to derive self-esteem than people with a harmonious passion such that they should experience self-esteem fluctuations as a function of their performances in their passionate activity. This study tested this hypothesis. Using self-reports, results first showed that the more people have an obsessive passion the more they report experiencing self-esteem fluctuations that covary with their performances in their passionate activity. In contrast, people with a harmonious passion did not report experiencing more, or less, self-esteem fluctuations. Second, hierarchical linear modeling confirmed that, in a real-life setting, the more people report an obsessive passion toward a card game, the greater is the impact of performance on their state self-esteem. Taken together, these findings suggest that obsessive, but not harmonious, passion triggers contingencies between people's self-esteem and their passionate activity. Copyright © 2011 John Wiley & Sons, Ltd.