Background: Limited research has investigated whether replacing psychiatric diagnosis with psychological formulation-based approaches has implications for lay attitudes to mental health. The present study investigates experimentally whether presenting psychosis in terms of a schizophrenia diagnosis vs. formulation narrative affects stigma and treatment attitudes in the general public.Method: The study employed a between-groups experimental vignette design, with data collected online. 351 participants (64.1% female, aged 18–66, ) read a vignette about a person experiencing psychosis, defined with either a diagnosis of schizophrenia or a narrative-based formulation. Participants completed a battery of scales measuring their attitudes to the vignette character (social distance, attribution, recommended treatment options, mental help-seeking attitudes).Results: Desired social distance was significantly greater in participants exposed to the diagnostic label of schizophrenia. The schizophrenia label led participants to rate medical care as significantly more helpful relative to the formulation condition but did not affect ratings of specialist or community care or mental help-seeking attitudes.Conclusions: These findings suggest that a psychological formulation approach may slightly lessen stigma-related attitudes, relative to traditional diagnostic systems. Popularisation of formulation models need not compromise general orientations to help-seeking or perceived helpfulness of specialist care but may lead to less medicalised treatment preferences.