In the past 10years, live-streaming services have gained huge popularity. Streamers usually play video games and complement their performance with commentary. We examine the role of this streamer commentary on state aggression in Czech adolescents who were randomly assigned into one of the three experimental groups (i.e. aggressive commentary, non-aggressive commentary, no commentary). The findings suggest that a short-term streamer’s commentary has no effect on affective and cognitive state aggression. In addition, the experimental conditions did not moderate any effects of personal traits (i.e. aggression, empathy) and long-term environmental factors (i.e. exposure to violence, watching violent streams, playing violent video games) on state aggression. We found that trait aggression, trait affective empathy and long-term exposure to violence were positively associated with state aggression, whereas trait sympathy was negatively associated with state aggression. The findings enrich the research with evidence for the lack of influence of streamer commentary on viewer aggression.