Previous research showed that the individual tendency to believe in conspiracy theories is related to various social, personality, and cognitive variables. Moreover, it may be a reflection of a broader individual tendency for epistemic irrationality, which drives also other pseudoscientific and paranormal beliefs. However, the relation between conspiracy belief and reasoning ability (fluid intelligence; Gf) was not sufficiently studied, even though Gf is crucial to how individuals think and reason. Using confirmatory factor analysis, we found the robust link between conspiracy belief and other irrational beliefs. All the irrational beliefs were also substantially related to close-minded cognitive style. However, Gf explained only below 2% of variance in conspiracy belief, even though it significantly predicted other irrational beliefs. These data suggest that effective reasoning cannot prevent even highly intelli-gent people from endorsing conspiracy theories.