A substantial proportion of line-up identifications involving child eyewitnesses in the UK are conducted by police officers wearing uniform. This study examined the possibility that wearing a uniform constitutes an authority cue that adversely affects a child's ability to make accurate eyewitness identifications. Sixty participants aged 9–10 years old witnessed a staged crime and were later asked to identify a ‘burglar’ from a simultaneous line-up using a 2 (uniform: present vs. absent) × 2 (target: present vs. absent) design. Children in the uniform present conditions made significantly more choices than children in the uniform absent conditions. More importantly, in the presence of a uniform, children made significantly more false identifications in target-absent line-ups. Analysis of supplementary, identification-related variables (identification time and confidence, state anxiety) suggested that (1) the children experienced uncertainty if the target was absent from the line-up, but (2) this uncertainty was not expressed when the line-up administrator wore a uniform, leading to an increase in false identifications. Implications for line-up administration procedures for children are discussed. Copyright © 2009 John Wiley & Sons, Ltd.