Psychological inoculation has proven effective at reducing susceptibility to misinformation. We present a novel storytelling approach to inoculation against susceptibility to the conjunction fallacy (d[subscript meta-analysis] = 0.82), a known cognitive predictor of conspiracy beliefs. In Study 1 (Pilot; N = 161), a narrative inoculation (vs. control) reduced susceptibility to conjunction errors, and in turn, conspiracy beliefs regarding government malfeasance. In Study 2 (main experiment; N = 141; pre-registered), two separate narrative inoculations (vs. control) directly reduced susceptibility to conjunction errors, and indirectly reduced conspiracy beliefs regarding extra-terrestrial cover-ups. In addition, the inoculation messages improved detection of both real and fake news ('truth discernment'). We discuss theoretical and practical implications, including the use of inoculation to induce critical thinking styles, and tailoring inoculations that may suit storytelling mediums.