The purpose of this paper is to explore negative peer interactions in foster care. Looked after children and young people have highlighted the impact of negative peer interactions, and especially peer violence and intimidation, on their care experiences. However, to date, no specific fostering research has addressed this important issue. In response to this gap, we undertook focus groups with 32 foster carers in the South West of England. Group discussions were semi‐structured based around the issue of negative peer interactions in foster care. The analysis revealed five main associated themes: the impact on the carers' birth children; a lack of placement planning; inadequate referral information; a negative view of social work support; and insufficient external interventions. Copyright © 2015 John Wiley & Sons, Ltd. ‘We undertook focus groups with 32 foster carers in the South West of England’ Key Practitioner Messages Negative peer interactions, particularly violence, were a major concern for foster carers, especially if they negatively impacted on the welfare of carers' birth children. An absence of pre‐placement referral information on negative peer interactions was commonly reported and placed all children in the fostering household at risk. Associated social work support and external interventions were often perceived as lacking and inadequate. Fostering procedures, review and decisions need to recognise the impact of peer violence on all members of the fostering household.