Issue AddressedThere is considerable evidence that public stigma around mental illness inhibits help‐seeking for mental health problems. Hence there have been many interventions and campaigns designed to reduce stigma around mental illness. However, as far as could be ascertained, none of these stigma reduction interventions has reported any substantial impact of reducing stigma on people's mental health help‐seeking behaviours. The aim of this paper is to report on the impact of the Act‐Belong‐Commit positive mental health promotion Campaign on help‐seeking via increasing perceived openness around mental health and reducing perceived stigma around mental illness.MethodsState‐wide computer assisted telephone interviews (CATIs) of the general adult population were undertaken in 2018 and 2019 (N = 600 adults per year). The questionnaire included measures of respondents' awareness of the Act‐Belong‐Commit Campaign, their beliefs about the Campaign's impact on mental illness stigma and openness around mental health issues, and whether they had sought help for or information about a mental health problem as a result of their exposure to the Campaign.ResultsThose who believed the Act‐Belong‐Commit Campaign increased openness around mental health issues were significantly more likely than those not holding this belief to have sought information about mental health and to have sought help for a mental health problem as a result of their exposure to the Campaign. Those who believed the Act‐Belong‐Commit Campaign decreased stigma around mental illness versus those not holding this belief were significantly more likely to have sought information, and more likely, but not significantly so, to have sought help as a result of their exposure to the Campaign. Overall, the effect was slightly greater for increased openness.ConclusionAs far as we are aware, these are the first reported findings of a positive impact on mental health help‐seeking behaviours as a result of a population‐wide mental health promotion Campaign being seen to have increased openness around mental health and decreased stigma around mental illness.So What?These findings suggest that accompanying specific stigma reduction interventions with a broad‐based, population‐wide, positive mental health promotion Campaign such as the Act‐Belong‐Commit campaign, could amplify these interventions' impact on help‐seeking by increasing openness about mental health issues.