Lone‐actor terrorists are very often presented as emotionally and/or cognitively impaired—yet is it really the case? The present article provides the first rigorous assessment of the hypotheses according to which a high level of negative emotions, especially anger, and a lack of cognitive flexibility and complexity play a role in lone‐actor terrorists’ violent actions. Using a sample of lone‐actor terrorists’ writings, we use the LIWC (a fully automated language use analysis software) to compare terrorists’ cognition and emotion with those of other control groups, most notably nonviolent radical activists. Results strongly support the first hypothesis but clearly refute the second one, suggesting that lone‐actor terrorists are in fact characterized by a specific combination of high‐anger and high‐cognitive complexity. These method and results lay the groundwork for a more systematic and nuanced analysis of the psychology of terrorists, which is currently in a deadlock.