Historical records suggest that the political extremes—at both the “left” and the “right”—substantially endorsed conspiracy beliefs about other-minded groups. The present contribution empirically tests whether extreme political ideologies, at either side of the political spectrum, are positively associated with an increased tendency to believe in conspiracy theories. Four studies conducted in the United States and the Netherlands revealed a quadratic relationship between strength of political ideology and conspiracy beliefs about various political issues. Moreover, participants’ belief in simple political solutions to societal problems mediated conspiracy beliefs among both left- and right-wing extremists. Finally, the effects described here were not attributable to general attitude extremity. Our conclusion is that political extremism and conspiracy beliefs are strongly associated due to a highly structured thinking style that is aimed at making sense of societal events.