Using a sample of 887 volunteer emergency service workers in South Australia, we conducted a study based on the JD-R framework to examine the roles of three mediators in the relationship between job characteristics and volunteer well-being. These were (i) exhaustion as a mediator in the relationships between job demands and both poor mental health and turnover intentions; and (ii) work engagement and organizational connectedness as mediators in the relationships of job resources (training and organizational support) with happiness and turnover intentions. Organizational connectedness, a relatively new construct, is a positive state of well-being that involves an emotional connection with other workers, with service recipients and with aspects of the task and the organization's values. Results indicated that all three mediators were important in explaining volunteer well-being. Specifically, job demands were positively related to exhaustion, which, in turn, was linked to ill-health and turnover intentions. Job resources were positively related to work engagement and organizational connectedness, which were, in turn, negatively related to turnover intentions. However, while organizational connectedness mediated the relationship between job resources and happiness, this was not the case for work engagement. The roles of these variables in future research in paid and voluntary work are discussed.