Global climate change and the COVID-19 pandemic that are among the most pressing societal crises share multiple links. It has been shown for instance, that the measures to fight against the coronavirus may impact (at least for a while) greenhouse gas emissions. Moreover, the COVID-19 can serve as a prototypical example for climate change, demonstrating how global crises may become personally relevant and certain. Here, our aim was to investigate whether explicit reference to the COVID-19 crisis in communication messages on global climate change could enhance message effectiveness. Through two pre-registered studies (Ntotal = 651), we examined whether the use of factual elements stressing the certainty dimension of the COVID-19 pandemic (Study 1) or the use of arguments linking COVID-19 and climate change framed in terms of “positive” or “negative” outcomes (Study 2) could impact the effectiveness of climate messages. Results did not show that messages aiming to increase the certainty of the climate crisis by linking it to the COVID-19 pandemic increased perceived message effectiveness. However, we have found that emotional framing influenced perceived message effectiveness, but not pro-environmental behaviour. Results are discussed in terms of the impact of the concepts of certainty, message framing and emotions on climate change communication.