In this paper, we examine the relationship between people's actual interpersonal sensitivity (such as their ability to identify deception and to infer intentions and emotions) and their perceptions of their own sensitivity. Like prior scholars, we find the connection is weak or non-existent and that most people overestimate their social judgment and mind-reading skills. Unlike previous work, however, we show new evidence about who misunderstands their sensitivity and why. We find that those who perform the worst in social judgment and mindreading radically overestimate their relative competence. We also find origins of these self-estimates in general narcissistic tendencies toward self-aggrandizement. We discuss evidence from two studies, one involving the Interpersonal Perception Task (the IPT-15) and another focusing on inferences about partners after a face-to-face negotiation exercise. In both cases, actual performance did not predict self-estimated performance but narcissism did.