There are various studies on mental health literacy which examine lay people’s knowledge and understanding of various mental disorders. Many are interested in beliefs about cause, manifestation and cure as well as the relationship between those beliefs. This study examines lay beliefs regarding the manifestations, aetiology and treatment of Narcissistic Personality Disorder (NPD), and their determinants using a questionnaire divided into three parts. Participants (N = 201) answered 45 attitudinal statements designed for this study regarding NPD. They consisted of 18 manifestation items, 15 aetiology items and 12 treatment items referring to NPD. They also completed the Narcissistic Personality Inventory. Each section of the questionnaire was factor analysed to determine the structure of those beliefs. Factors derived from a principle component analysis of lay beliefs demonstrate poor knowledge of NPD. Factors derived from the manifestations, aetiology and treatment section were modestly and coherently correlated. No demographic factors correlated with all aspects of mental health literacy and lay theories. People are surprisingly misinformed about NPD. They believed that narcissists manifested superficiality and social problems, business abilities and fragility. No distinction was made between biological and psychological causes or genetics and early negative events. Inability to identify NPD may account for many reports of sub-clinical narcissism being associated with leadership derailment.