We develop a decision-making tool for the management of invasive alien trees in the Cape Floristic Region (South Africa). We conducted numerous interviews and workshops with managers in order to understand how management actions take place and what the most influential variables are. This information was used to design of a prioritization tool, subsequently incorporated into a spread model to assess the effects of using different management strategies. This research reflects a successful interaction between scientist and management whose common goal is to tackle biological invasions more efficiently.