The present study examined mental health literacy among the British general public using the overclaiming technique, where participants rate for familiarity a series of items, some of which are foils resembling real items. In total, 344 Britons rated for familiarity 30 mental health disorders, of which six were foils, and also completed measures of the Big Five personality factors, self-rated intelligence, self-reported knowledge of psychiatry, psychiatric skepticism, and their personal details. Using signal detection analysis, responses on the overclaiming measure were used to compute an accuracy index (accuracy in distinguishing real mental health disorders from foils) and a response bias (the tendency to response affirmatively to both real disorders and foils). Preliminary analysis showed that there were no significant sex differences on either the accuracy or response bias indices. Further analyses showed that greater accuracy was significantly predicted by higher self-rated intelligence, greater knowledge of psychiatry, and lower psychiatric skepticism. These results are discussed in terms of the benefits of using the overclaiming technique and signal detection analysis in the study of mental health literacy.