The current studies explored the social consequences of exposure to conspiracy theories. In Study 1, participants were exposed to a range of conspiracy theories concerning government involvement in significant events such as the death of Diana, Princess of Wales. Results revealed that exposure to information supporting conspiracy theories reduced participants’ intentions to engage in politics, relative to participants who were given information refuting conspiracy theories. This effect was mediated by feelings of political powerlessness. In Study 2, participants were exposed to conspiracy theories concerning the issue of climate change. Results revealed that exposure to information supporting the conspiracy theories reduced participants’ intentions to reduce their carbon footprint, relative to participants who were given refuting information, or those in a control condition. This effect was mediated by powerlessness with respect to climate change, uncertainty, and disillusionment. Exposure to climate change conspiracy theories also influenced political intentions, an effect mediated by political powerlessness. The current findings suggest that conspiracy theories may have potentially significant social consequences, and highlight the need for further research on the social psychology of conspiracism.