Purpose This paper aims to describe a case that has worked with community aiming to prevent koala deaths and injuries across known causes including dogs. Design/methodology/approach Over a 6½-year period, a project team has applied the Co-create–Build–Engage (CBETM) process initially delivering a proof-of-concept pilot programme for one threat faced by koalas, which was later scaled to citywide delivery. This approach is now being extended across 12 local government areas, and the author’s team is now working across all preventable threats faced by koalas’ regionwide. Leave It is now nested as one behaviour change project in a wider project delivered across Southeast Queensland, in partnership with Queensland Government, 12 local government areas, community groups and other organisations. Findings Underpinned by the pathway to impact and CBETM processes, this paper describes how the 3½-year Leave It project reduced koala deaths from dog attacks by 40% in the Redland City Council area. A reduction in koala deaths will contribute to a measurable increase in the local koala population across successive generations delivering lasting impact. Research limitations/implications This paper provides an overview of links between inputs, activities, outputs and outcomes to impact. Robust koala population data is needed to precisely measure impact over time. Practical implications One female koala joey saved equates to seven new koalas in the next generation and prevention of koala deaths can be achieved when people can be motivated to take action. Originality/value This paper reflects on 6½ years of experience applying marketing to deliver changes in people’s behaviour that protect koalas. A high-level overview of the strategic and operational marketing efforts that have been and continue to be applied is described.