The ability to figure out whether a person is being honest or deceitful is an important part of social competence. Reactions to deceit may however differ depending on whether one is being deceived oneself or observes a deceitful exchange between others. In the present study, we investigated whether personal involvement influenced the neural responses associated with the detection of deceit. Subjects watched videos of actors lifting a box and judged whether the actors had been misled about the real weight of the box. Personal involvement was manipulated by having the participants themselves among the actors. The critical finding was that there was activity in amygdala and fusiform gyrus only for the condition in which participants observed themselves being deceived. In contrast, the superior temporal sulcus and anterior cingulate cortex were activated irrespective of whether the participants detected that the experimenter had deceived themselves or another. These four brain areas are all interconnected and are part of the discrete neural system subserving social cognition. Our results provide direct evidence, using judgments of deceit in a social context, that the crucial factor for amygdala activation is the involvement of the subjects because they are the target of the deceit. We interpret the activation of the amygdala in this situation as reflecting the greater affective reaction when one is deceived oneself. Our results suggest that when one is personally involved, deceit is taken as a potential threat.