This study examined whether individual differences in causality orientation moderate the effects of monetary reward and choice on perceived competence, which affect intrinsic motivation in turn. Causality orientation refers to an individual's tendency to experience or interpret events in a social context in a specific way and to behave accordingly, and is directly related to the development of intrinsic motivation. We randomly assigned 103 undergraduate students to one of four conditions: reward (reward vs. no reward) x choice (choice vs. no choice). Participants were presented with puzzles to solve in the experimenters' presence, and they were free to continue working on it once the experimenters left the room. We measured the time spent on solving puzzles when participants were free to choose other activities, and used self-reported feedback on task enjoyment as an index for intrinsic motivation. We also measured perceived competence as a mediator. Task enjoyment was unaffected by reward in participants with high autonomy orientation, but dropped significantly in participants with low autonomy orientation. Choice over task increased perceived competence in participants with high autonomy orientation, but lowered perceived competence in the case of low autonomy orientation. We found no significant effects for time spent on puzzles. The present study contributes to current understandings of the causes of performance differences in various settings.