This article contributes to knowledge of how environmental disasters affect ecomodernist beliefs, i.e. the view that technology can solve environmental problems. Such beliefs in the general public are key to build mass support for environmental policies relying on large‐scale scientific solutions, but their stability is poorly understood. We argue that ecomodernist beliefs are more malleable than assumed and can be altered through events that highlight risks arising from a reliance on technological solutions. This study leverages that the Fukushima‐Daiichi accident happened during the fieldwork of a 2011 public opinion survey in Israel. The analysis suggests that ecomodernist beliefs were negatively affected by this unexpected tragedy. Consistent with expectations, we report stronger impact among people with more education. We document similar effects from a controlled survey experiment in the US and Israel, suggesting that these results are generalizable. Our findings are relevant beyond rare environmental disasters as they have implications for how ecomodernist beliefs might be formed and changed.