This study examined the effects of dispositional aspects of identity on intentions and behavior in the context of the theory of planned behavior (TPB) for three health behaviors: exercise, dieting, and binge drinking. It was expected that personal and social identity orientations would predict intentions via the mediation of attitude/perceived behavioral control (PBC) and subjective norms, respectively. It was also hypothesized that aspects of identity will predict behavior directly, reflecting spontaneous, unplanned influences on behavioral engagement. Participants (N = 525) completed measures of personal and social identity in conjunction with measures of attitude, subjective norm, PBC, and intention from the TPB for the three behaviors. Structural equation models showed that personal identity influenced PBC for all three behaviors, affected attitude and subjective norms positively in the exercise sample, and influenced attitude and subjective norms negatively in the binge drinking sample. Social identity positively affected attitudes, subjective norms, and PBC in the binge drinking sample only. There were no direct effects of the identity constructs on intentions and behavior. Results are in keeping with the TPB and suggest that these identity aspects are influential in the decision-making process for these health behaviors.