Worry and risk perception were integrated into the theory of planned behavior (TPB) within health and non-health domains (flossing and academic coursework, respectively). Models were estimated and replicated in 2 undergraduate samples (ns = 191 and 309), with effects of worry and risk on intentions expected to occur primarily through attitudes. Past behavior was modeled through effects on all TPB constructs and through interactions with worry and risk. Worry positively predicted intentions and attitudes (and norms in the non-health domain) for those at the lowest levels of prior behavior. Risk perceptions negatively predicted intentions and self-efficacy (and attitudes in the health context) also for those at low levels of prior behavior. Implications for further theory development are discussed.