Objective: To estimate awareness of pre-diabetes or type 2 diabetes and associated factors in people with psychosis, a known high-risk group. Methods: Cross sectional analysis of a national sample with psychosis who were aged 18–64 years, gave a fasting blood sample (n = 1155), had pre-diabetes or diabetes based on testing (n = 359) and reported if they knew they had high blood sugar or diabetes at survey (n = 356). Logistic regression was used to identify factors associated with awareness of pre-diabetes or diabetes prior to testing. Results: The prevalence of pre-diabetes (19.0% 219/1153) or type 2 diabetes (12.1%, 140/1153) was 31.1% (359/1153); 45% (160/356) were known prior to testing. Factors associated with detection were higher fasting blood glucose, older age, a perception of poor health, severe obesity, dyslipidaemia or treatment with a lipid regulating drug, a family history of diabetes, Aboriginal or Torres Strait Islander descent, decreased cognitive functioning, regional economic disadvantage, treatment with an antihypertensive drug, and an elevated 5-year risk for cardiovascular disease. The prevalence of undiagnosed pre-diabetes/diabetes was highest in those aged 25–34 years at 34.2%. Conclusions: Clinical detection of pre-diabetes or diabetes in people with psychosis was strongly dependent on established risk factors for type 2 diabetes in the population but not on current antipsychotic drug treatment or psychiatric case management which should ensure regular screening. Screening must become a clinical priority and should not wait until age 40.