Communicating possible effects of climate change inevitably involves uncertainty. Because people are generally averse to uncertainty, this activity has the potential to undermine effective action more than stimulate it. The present research considered how framing climate change predictions differently might moderate the tendency for uncertainty to undermine individual action. Two studies (Ns. = 88 and 120) show that higher uncertainty combined with a negative frame (highlighting possible losses) decreased individual intentions to behave environmentally. However when higher uncertainty was combined with a positive frame (highlighting the possibility of losses not materializing) this produced stronger intentions to act. Study 2 revealed that these effects of uncertainty were mediated through feelings of efficacy. These results suggest that uncertainty is not an inevitable barrier to action, provided communicators frame climate change messages in ways that trigger caution in the face of uncertainty.