Self-enhancement is a pervasive motivation that manifests broadly to promote and protect the positivity of the self. Research suggests that self-enhancement is associated with improved task performance. Untested, however, is whether that association is causal. The present research experimentally manipulated self-enhancement to examine its causal effect on task performance. Participants in 5 experiments were randomly assigned to self-enhance or not before completing a creativity task (Experiments 1–4) or pain-inducing cold-pressor task (Experiment 5). Results indicate that self-enhancing (but not self-effacing) on a dimension relevant (but not irrelevant) to the task facilitated performance. Furthermore, the data were consistent with the possibility that the performance facilitating effect of self-enhancement was mediated through task-relevant self-efficacy.