A 44-item questionnaire was created to examine pre-service teachers' knowledge and perceptions of the impact of mitigative climate change actions and how willing they are to undertake these actions. Responses (N = 224) were collected from pre-service teachers at the University of Eastern Finland. The findings show that pre-service teachers have a very low level of knowledge of the impact of different mitigative climate change actions. Furthermore, the students tend to overestimate the carbon footprint of low-impact actions and underestimate the carbon footprint of high-impact actions and they are unable to make a clear distinction between low- and high-impact actions, though the impact of the high-impact actions may be many times greater than those of low-impact actions. In general, pre-service teachers were willing to take low-impact actions, somewhat willing to take mid-impact actions, but reluctant to take the highest-impact actions. Knowledge of the impact of actions did not correlate with willingness to act, possibly due to low levels of knowledge. Some correlation between confidence in knowledge and willingness to act was found. This article discusses the importance of considering confidence in knowledge in future research examining the relationship between knowledge and action. The implications of the findings on teacher education and environmental education are also discussed.