The use of e-cigarette or vape devices is a growing concern on an international scale, given the devices' addictive nature and questions regarding their short- and long-term health impacts. Their use is especially an issue in young people, many of whom have little or no previous nicotine use experience. This study tested an integrated dual process model in 363 young Australian undergraduates where prospectively measured e-cigarette use was predicted by the psychological constructs of the theory of planned behavior, supplemented with risk perception, e-cigarette dependence, habit, and implicit attitude. Intention to use an e-cigarette was predicted by affective attitude, subjective norm, and e-cigarette dependance, but not instrumental attitude, perceived behavioral control, or risk perception. E-cigarette use was predicted by e-cigarette dependance, intention, habit, implicit attitude, and previous nicotine use, although perceived behavioral control did not directly predict behavior nor moderate the intention-behavior relationship. Current findings provide evidence for important psychological predictors of e-cigarette use, signposting potential intervention targets. Specifically, interventions may benefit from using strategies that tap affective or normative beliefs alongside automatic constructs and dependence, while focusing less on beliefs about the health impacts of e-cigarettes or control over using.