Résumé : Research over decades has demonstrated that emotions interact with various cognitive functions. In contrast with first-order cognition, studies exploring the influence of emotions on metacognition (i.e. the ability to reflect on and control our own cognitive processes) are still very sparse. The present thesis investigated how several emotional states influence metacognitive performance. We have considered different emotions (such as happiness, anxiety or depression) and different metacognitive measures (such as subjective difficulty, overall confidence or metacognitive efficiency). Altogether, our results provide evidence that emotional states can specifically influence the way individuals evaluate their own decisions, which exist independently of their first-order performance. Furthermore, our findings suggest that different emotions each exert a different impact on metacognition. For instance, inducing a sad mood reduces overall confidence, while induced anxiety leads to a decrease in metacognitive efficiency. However, predicting how an emotion will influence metacognition remains very difficult, as this seems to depend on many parameters.