The "Make Healthy Normal" obesity prevention mass media campaign was implemented in New South Wales, Australia from 2015 to 2018. This study evaluated Phase 2 (2017-18) of that campaign, using three cross-sectional online surveys with men aged 18-54 years (n = 4352) and six focus groups with men aged 35-54 years and parents with children aged 5-12 years (n = 38), reflecting the campaign's target audiences. We used linear and logistic regressions to examine changes over time in key outcomes, consistent with the campaign's theorized hierarchy of effects. Focus group data were analysed thematically and integrated with survey results at the interpretation stage. Survey results showed reasonable prompted recognition, although unprompted recall remained low, and there were no consistent, positive shifts in other outcomes, including behaviour. Focus group results suggested that this was because the campaign's messages, while considered clear and relevant, did not address the constraints participants experienced that made change difficult. Hence, the campaign by itself was unlikely to lead to behaviour change. We need to reconsider the role of campaigns in addressing multi-determined and complex problems. Evaluations should reconsider metrics of success, as they may not immediately result in behaviour change, especially in the absence of complementary policy and environmental strategies.