How can individuals’ responses to the coronavirus disease-19 (COVID-19) pandemic be used to inform constructive responses for climate action? We present an exploratory, mixed-methods investigation ( N = 1784 US adults) into similarities and differences in individuals’ reactions to COVID-19 and climate change in June 2020. Participants identified many similarities between the issues, indicating that both are harmful to public health, politically polarizing, have global impacts, and have solutions. Participants also perceived many differences between the two threats: many perceived COVID-19 as medical, natural, and on a shorter timescale, while many perceived climate change as environmental, human caused, and on a longer timescale. Emotional reactions to each topic predict topic-relevant behaviors, but more strongly, and with a broader range of emotional reactions, for climate change than COVID-19. Open-ended responses show that hope was elicited for both issues in response to contemplating taking collective and individual actions, and despair was elicited for both issues in response to perceiving that others do not take the issues seriously. Finally, participants perceived that they were engaging in relatively more COVID-19 mitigation behaviors and some climate change mitigation behaviors than others (i.e., the “better-than-average” effect). Many participants believed others were relatively unconcerned about both threats because of the invisibility of the threats, ignorance, and elite cues (e.g., then-President Trump downplaying the threat). Supplementary Information The online version contains supplementary material available at 10.1007/s10584-021-03143-8.