Few studies investigate what members of the general population know about individuals with autism. Only one study has previously investigated how beliefs about autism differ from those about other psychiatric disorders. This study surveyed a convenience sample of the general adult population, within the Northern Region of Denmark, about their knowledge, attitudes and beliefs about individuals with autism and schizophrenia. The respondents (N = 440) possessed basic knowledge and were able to differentiate between the two disorders. Schizophrenia was associated with perceived danger (32.8%), while autism was associated with high intelligence (40.1%) and creativity (27.3%). Respondents were more positive towards interacting with individuals with autism (p < 0.001), but desire for social distancing was pronounced for both disorders in more intimate relationships. Significantly, more respondents reported that they would find it difficult and feel ashamed with regard to being diagnosed with schizophrenia (p < 0.001). Conversely, respondents significantly reported being more likely to elaborate on their diagnosis of autism to their colleagues (p < 0.001). Perceived dangerousness decreased the willingness for social interactions, while knowing someone with autism or schizophrenia increased the willingness to socially interact. Misconceptions and stigma must be addressed in order to minimize the social stigma and rejection associated with these disorders and ultimately improve the quality of life and psychological well-being of affected individuals and their families.