Utilizing two studies, determinants of travelers’ carbon offsetting attitudes and the role that gender plays in cognitive appraisal and attitude formation are examined by exploring the interactions between knowledge, credibility, and trust and their relative impacts on behavioral intentions. Findings suggest that objective knowledge, subjective knowledge, trust, and credibility impact attitudes in dramatically different degrees. Females are found to be higher in objective knowledge, credibility of climate science, and carbon offsetting attitudes, whereas males are found to be higher in subjective knowledge. Knowledge is found to be not only an imperfect predictor of carbon offsetting attitudes but can negatively influence attitudes through indirect effects on trust and perceived credibility. Furthermore, travelers who process information heuristically (primarily males) will have significantly different responses to stimuli than travelers who process information systematically (primarily females). Implications for message framing and possible interventions to increase participation levels in voluntary carbon offset programs are discussed.