The dualistic model of passion defines passion as a strong inclination toward a self-defining activity that a person likes and values and in which he or she invests time and energy. The model proposes two distinct types of passion: harmonious and obsessive passion that predict adaptive and less adaptive outcomes respectively. In the present research, we were interested in assessing both the negative and positive consequences that can result from gaming. Participants (n = 222) were all players involved in massively multiplayer online games. They completed an online survey. Results from a canonical correlation revealed that both harmonious and obsessive passion were positively associated with the experience of positive affect while playing. However, only obsessive passion was also positively related to the experience of negative affect while playing. In addition, only obsessive passion was positively related to problematic behaviors generally associated with excessive gaming, the amount of time spent playing, and negative physical symptoms. Moreover, obsessive passion was negatively related to self-realization and unrelated to life satisfaction. Conversely, harmonious passion was positively associated with both types of psychological well-being. This general pattern of results suggests that obsessive passion for gaming is an important predictor of the negative outcomes of gaming, while harmonious passion seems to account for positive consequences. Future research directions are discussed in light of the dualistic model of passion.