Anti-stigma programme evaluations primarily measure knowledge and attitudes, and rarely assess behaviour. This study describes perceived and self-reported avoidance, discrimination and positive treatment using data from the 2017 Attitudes to Mental Illness survey. A nationally representative quota sample of 1720 English participants were interviewed about mental health-related knowledge and attitudes, reported and intended contact with people with mental health problems, awareness of the Time to Change anti-stigma programme and knowledge of anyone with a mental health problem. Participants who knew someone were asked how they thought the person was treated in different life areas, and whether they had avoided the person, treated them unfairly or treated them more positively. 30.1% of respondents knew someone with a mental health problem. Most believed the person had been treated fairly across various life domains. 5.1% of participants reported avoiding the person, 2.1% reported unfair treatment, and 58.1% reported positive treatment. Less stigmatising attitudes were associated with reduced avoidance and discrimination. Greater knowledge and reported contact were associated with positive treatment. Anti-stigma campaigns can reduce discrimination or increase positive treatment by targeting knowledge, attitudes and awareness of people with mental health problems. Evaluations should measure discrimination and positive treatment to fully assess behavioural change.