In-vehicle information system (IVIS) use while driving has raised concerns about driver distraction, especially for young drivers. To understand better their psychological factors, an extended theory of planned behavior (TPB) was employed to predict young drivers’ IVIS use intentions and behavior while driving. A two-wave longitudinal survey was conducted to explore the temporal effects of ‘intention–behavior’ causality. At Time 1, 236 qualified participants completed a main questionnaire assessing the standard TPB constructs (attitude, subjective norms, and perceived behavior control) and the extended constructs (descriptive norms, moral norms, and perceived risks). At Time 2, 145 follow-up questionnaires measuring self-reported behavior were successfully administered. The hierarchical multiple regression analyses showed that the standard constructs account for 36.5% of the intention variance and 41.2% of the behavior variance. The extended constructs additionally contributed 20.3% of intention variance. All variables were identified as significant predictors of intentions, except for perceived crash risks and perceived risks of being caught and fined. The sole significant predictor of prospective behavior was intention. Theoretically, the findings further support the efficacy of the TPB in explaining IVIS use while driving. Practically, it is helpful to design non-legal interventions that sustainably reduce young drivers’ engagement in IVIS-related distractions.