In this observational study, conducted in a penitentiary setting in the Netherlands with detained male adults, we investigated if violent offenders (n = 71) show a stronger tendency to interpret ambiguous facial expressions on a computer task as angry rather than happy, compared to non-violent offenders (n = 14) and to a control group of healthy volunteers (n = 32). We also investigated if hostile perception of facial expressions is associated with specific characteristics of aggression, such as proactive and reactive aggression, based on multiple self-report questionnaires (Buss-Perry Aggression Questionnaire, Reactive-Proactive Aggression Qurestionnaire) and behavioural observations (Social Dysfunction and Aggression Scale - SDAS, rated once a week over a period of 4 weeks). Other relevant variables, such as psychopathic traits (Psychopathic Personality Inventory-revised), intelligence (Raven Standard Progressive Matrices), attention (Trail Makint Test-A/B) and a tendency to jump to conclusions (beads-in-a-jar task) were also assessed. The study protocol was not published online. Participants completed a neuropsychological test battery, of which the threshold score of the emotion perception task was the primary outcome measure. The threshold score of the emotion perception task is scored so that lower scores reflect a tendency to rate the faces as angry, while higher scores reflect a tendency to rate the faces as happy. The data dictionary defines the contents of the data sheet comprehensively. The data set comprises group, age-categories, data on the above mentioned questionnaires and neuropsychological tests (including threshold score). Conviction data were not included in the data file to ensure anonymity of the participants. The deposit includes the following files: Data Dictionary Data Sheet Data files and data dictionary can be opened in Excel or SPSS software.