Conspiracy theories explain complex world events with reference to secret plots hatched by powerful groups. Belief in such theories is largely determined by a general propensity towards conspirational thinking. Such a conspiracy mentality can be understood as a generalised political attitude, distinct from established generalised political attitudes such as right-wing authoritarianism (RWA) and social dominance orientation (SDO) (Study 1a, N = 497) that is temporally relatively stable (Study 1b and 1c, total N = 196). Three further studies (combined N = 854) show that in contrast to RWA and SDO, conspiracy mentality is related to prejudice against high-power groups that are perceived as less likeable and more threatening than low-power groups, whereas SDO and RWA are associated with an opposite reaction to perceptions of power. Study 5 (N = 1852) investigates the relationship of conspiracy mentality with political behavioural intentions in a specific catastrophic scenario (i.e. the damage to the Fukushima nuclear reactor after the 2011 tsunami in Japan) revealing a hitherto neglected role of conspiracy mentality in motivating social action aimed at changing the status quo. Copyright © 2013 European Association of Personality Psychology.