Background In accordance with the social information processing model, how adolescents attribute cause to a particular social situation (e.g., bullying) they witness or participate in, influences their online social information processing, and hence, how they will act in the situation. Objective The aim of the present study was to explore how older teenagers explain why bullying takes place at school, and whether there were any differences in explaining bullying due to gender. Methods Two hundred and fifteen Swedish students in upper secondary school responded to a questionnaire. Mixed methods (qualitative and quantitative methods) were used to analyze data. Results The qualitative analysis resulted in three main categories and nine subcategories regarding accounts of bullying causes. According to the findings, the youth explained bullying much more often with individualistic explanations (bully attributing and victim attributing) than nonindividualistic explanations (social context attributing). Furthermore, girls tended to provide a greater number of bullying explanations and were more likely to attribute bullying causes to the bully and the victim, as compared to boys. Conclusions The findings provide insights into older teenagers' understanding of why bullying occurs in school. The study also identified some gender differences but also some mixed findings regarding gender differences in comparison with previous research with younger participants. The authors concluded that more research has to be done to investigate age and gender differences.Keywords: Bullying; Peer victimization; Teenagers' perspectives; Attribution; Gender Introduction Bullying, commonly defined as repeated aggression or harassments directed at targets who are disadvantaged or less powerful in their interactions with the bully or bullies (Jimerson et al. 2010;Olweus 1993;Terranova 2009), is a widespread problem in schools that students across the world report seeing or experiencing (e.g., Borntrager et al. 2009;Eslea et al. 2003). One way of enhancing our understanding of school bullying and hence generating more effective bullying prevention and intervention programs is to investigate students' perspectives and how they explain bullying because how they understand, interpret and attribute bullying has an impact on their reactions and behaviors if they see or become involved in bullying situations.In Crick and Dodge's (1994) social information processing (SIP) model, children and adolescents' assumptions and conceptions of social situations and people involved in these situations influence how they process social information and thus how they respond and act in these social situations (also see Dodge et al. 2006;Gifford-Smith and Rabiner 2004). Attribution is a cognitive process in which people infer causes of events. Causal reasoning involves assumptions of other people's qualities or characteristics and assumptions of situational dynamics (Fiske and Taylor 2008). How children and adolescents attribute cause to a particular socia...