Gamification has become a popular approach to blending learning with fun and enjoyable experiences. However, gamification research has been criticized for mostly focusing on game mechanics and related outcomes while paying little attention to the psychological processes that mediate the relationship between these mechanics and outcomes. Furthermore, the majority of existing gamification studies have focused on competitive game features. Thus, the full potential of cooperative gamification has yet to be explored. Given this background, the current study compared how gamified cooperation and competition impact task effort, learning achievement, motivation and social relatedness in English vocabulary learning with a mobile application. The study utilized Social Interdependence Theory to explicate the psychological processes in gamified cooperation and competition. 75 participants were randomly assigned to either the gamified cooperation or the gamified competition condition and studied English vocabulary for 14 days. No difference was observed between the conditions regarding task effort, learning achievement and motivation. However, social relatedness in the gamified cooperation group was significantly higher than in the gamified competition group. The current findings emphasize that the positive influence of gamified cooperation on creating meaningful connections amongst learners should not be ignored, even though it facilitates similar learning and motivational outcomes as gamified competition.