Staff loss and demotivation can be costly for unions. In this article the authors investigate factors influencing expected voluntary turnover, that is Intention to Leave (ITL), of union employees by conducting an online survey of 160 staff in three Australian unions. Moderated multiple regression analyses revealed that perceived organisational support, shortcomings in training and unmet intrinsic needs predicted ITL, after controlling for burnout, labour market mobility and intrinsic motivations. Critically, the results suggest an interaction effect involving training in some circumstances. Training buffered the impact of low support on ITL, however the adverse effect on ITL of organisational failure to meet staff expectations regarding service to members remained, independent of training. Implications for theory and practice are discussed, including the separate significance of resources and purpose.