Episodic volunteers (EVs) are vital for non-profit organization activities. However, theory-based research on episodic volunteering is scant and the determinants of episodic volunteering are not well understood. This study integrates the volunteer process model and three-stage model of volunteers' duration of service to explore determinants of EV retention. A cross-sectional survey of 340 EVs assessed volunteering antecedents, experiences, and retention. Social/enjoyment (ߠ= .17) and benefit (ߠ= -.15) motives, social norm (ߠ= .20), and satisfaction (ߠ= .56) predicted Novice EV (first experience) retention; satisfaction (ߠ= .47) and commitment (ߠ= .38) predicted Transition EV (2-4 years intermittently) retention; and supporting the organization financially (ߠ= .31), social norm (ߠ= .18), satisfaction (ߠ= .41), and commitment (ߠ= .19) predicted Sustained EV (5-6 years consecutively) retention. Integrated theoretical approaches appear efficacious for understanding EV retention. An Episodic Volunteer Engagement and Retention model is proposed for further testing in prospective work.