Increasing landholder participation in environmental programmes is often essential for achieving desired levels of restoration and protection, as well as the economic goals of efficiency and equity. Previous literature has identified sociodemographic property and attitudinal variables that influence participation. Using qualitative research, we identify variables relating to human capital (business orientation and information seeking behaviour) and social capital (trust in those delivering programmes and connectedness with other landholders) that have been seldom or never identified as influencing participation. New scales are developed and existing scales refined for measuring these constructs, and their influence on past and future participation is examined together with a range of other constructs. The effect of these variables is examined using a survey of Australian landholders, and the results demonstrate the primacy of variables relating to human and social capital in influencing past and future participation.