Conservationists often complain that their study species are ignored by donors. However, marketing theory could help understand and increase the profile and fundraising potential of these neglected species. We used linear regression with multimodel inference to analyse data on online behaviour from the websites of the World Wildlife Fund-US (WWF-US) and the Zoological Society of London's EDGE of Existence programme (EDGE), in order to understand how species traits and marketing campaign characteristics influenced flagship-based fundraising efforts. Our analysis accounted for species traits through variables such as appeal and familiarity, and marketing campaign characteristics through measuring the order in which the species were presented and the amount of information provided. We found that species traits were key for the WWF-US website, with appealing and threatened non-mammal species the most popular with donors. This was probably because WWF-US used well-known flagship species and so marketing had little impact. The EDGE website used a wider variety of species and in this case both species traits and the marketing campaign characteristics were important, so that appealing species and well-promoted species did best. We then predicted outcomes for a hypothetical EDGE fundraising campaign with varying degrees of marketing effort. We showed that additional marketing can have a large impact on donor behaviour, potentially increasing the interest of potential donors towards unappealing species by up to 26 times. This increase would more than equal the amount raised by campaigns using appealing species without additional promotion. Our results show marketing can have a large impact on donor behaviour and suggest there is scope for successful marketing campaigns based on a much wider range of species.