Abstract Background About 200 000 children in Sweden live in families where violence among adults occurs. About 10% of children have witnessed violence family violence Family violence is often more prevalent in low social status families. The present study describes adolescents that have witnessed threats of violence, abusive words or physical/sexual violence in their families, as well as the association between these types of violence and socio-economic factors. Methods Data from a school-based survey, in the County of Sörmland (2023), including 15-18-years-old students in 2023 were used. Witnessing family violence was measured by the following item “Have you experienced that an adult in your family has... 1) threatened to use violence against someone else in your family? 2) used abusive words, oppression, or been dominant or controlling against someone else in your family? 3) used physical violence against someone else in your family, such as hitting, pushing, kicking, or sexual violence”. Parental work status, the child’s living conditions and economic stress were used as socio-economic factors. Data were analysed by descriptive methods and logistic regressions. Results This study included 3 407 adolescents among which 19% had witnessed any type of family violence. The most prevalent type was witnessing abusive words, (17%), followed by physical/sexual violence (10%) and threats to use violence (9%). Witnessing any type of family violence was associated with all socio-economic variables in univariate analyses, the strongest association was found for having economic stress (OR = 3.30; 95% CI 2.72-4.01), in comparison to not having economic stress. Further adjustments for gender, grade, ethnicity, parental work status and living with both parents attenuated the association, OR = 2.50 (95% CI 2.03-2.07). Conclusions Two of ten adolescents have witnessed any type of family violence. These adolescents often belonged to families with low socioeconomic status making them vulnerable. Key messages • In this school-based study, 19 % of adolescents had witnessed any type family violence. Having witnessed abusive words was the most prevalent type of family violence. • There is as strong association between witnessing family violence hand having economic stress among adolescents. These adolescents need to be noticed in their particularly vulnerable situation.