Processes of self-justification were investigated in a field experiment among car drivers. High self-esteem was expected to reduce internal and external self-justification strategies. Dissonance was aroused by confronting respondents with the negative consequences of car driving either for others, that is, moral dissonance (e.g., environment, public health), or for themselves, that is, hedonistic dissonance (e.g., travel time). A third group served as a no-dissonance control group. Consistent with the predictions, no self-justification was found among high-self-esteem respondents. Low-self-esteem respondents displayed more external self-justification strategies in response to moral dissonance and internal self-justification strategies in response to hedonistic dissonance, although the latter effect was weaker. Results of Study 2 suggest that high-self-esteem respondents are less likely to engage in self-justification because they experience less discomfort after a self-threat. Together, the results illuminate the relation between self-esteem and self-justification and provide external validity for self-affirmation theory.