Dyslexia does not cause criminal behaviour, but it may worsen aggressive behaviour tendencies. In this study, aggressive behaviour and risk of future violence were compared between forensic psychiatric patients with and without dyslexia. Dyslexia was assessed using the Swedish phonological processing battery "The Pigeon". The patients filled in the Aggression Questionnaire, and trained assessors performed the risk assessments using HCR-20 version 2. Patients with dyslexia self-reported more aggressive behaviour compared with those without dyslexia. There was only a nearly significant tendency (p = 0.06) for the patients with dyslexia to receive higher scores in the HCR-20 compared with the patients without dyslexia, and phonological processing skills did not significantly predict aggression or risk of future violence. However, regression analyses demonstrated that poor phonological processing skills are a significant predictor of anger, which in turn significantly predicts risk of future violence. (Contains 1 table.)