The adverse impact of first episode psychosis (FEP) upon parents' quality of life (QoL) has been well documented. However, the determinants and levels of QoL remain poorly understood in siblings of young people experiencing FEP. This study aimed to characterise and establish the predictors of QoL for siblings of young people with FEP.Survey methodology was used to examine the experience of 157 siblings in the first 18 months of their brother or sister's treatment for FEP. The World Health Organisation Quality of Life Scale-Bref (WHOQOL-Bref) was used to assess siblings' QoL. A series of multivariate regression analyses were conducted to determine the relationships between illness characteristics and siblings' QoL.Younger sisters reported the lowest satisfaction of QoL. Older brothers were the most satisfied. When the young person with FEP had attempted suicide and/or had been physically violent, siblings reported less satisfaction in all domains of QoL. Living with the ill brother or sister resulted in less satisfaction in the social domain. Multivariate analysis showed that female gender was a significant factor in explaining the impact of illness-related variables on QoL, particularly suicide attempts.Suicide attempts and a history of violence impacted negatively on all four domains of QoL. Female siblings are at higher risk of reduced QoL and may be particularly vulnerable to the effects of suicide attempts and violence. These findings have significant implications for early, targeted interventions for this vulnerable group.