Predicting the willingness of people to engage in passive surveillance is crucial to the success of community-based efforts to manage invasive species and conserve native biodiversity. We draw on the marketing concept of involvement, which reflects the personal importance of an issue or behaviour, to understand and measure the motivation of members of the public to engage in passive surveillance. The usefulness of this concept was tested by analysing the responses of householders to surveys about their willingness to engage in passive surveillance for a purely environmental pest, Red-eared Slider Turtles (Trachemys scripta elegans), and their willingness to engage in passive surveillance for an economic and environmental pest, Argentine Ants (Linepithema humile), in New Zealand. We found that involvement influenced intentions, attitudes and surveillance behaviour for both invasive pests. We discussed the implications of these findings for (i) choosing between a surveillance strategy based on recruiting and training highly motivated members of the public and a strategy based on passive surveillance by any member of the public; (ii) growing the potential for passive surveillance by either increasing involvement with preventing the spread of a pest or increasing involvement with surveillance activities themselves; and (iii) determining the importance of convenient reporting mechanisms in promoting consistent reporting.