Background: Looked after children (LAC) are a unique clinical group who, as a result of multiple trauma and disrupted attachment in early life, often present with complex mental health needs. In order to develop a meaningful formulation and provide suitable treatment for these children, the assessment of mental health difficulties in LAC is paramount. However, limited measures have been developed with LAC in mind and very few have been validated in this population. A recent literature review (Denton, Frogley, Jackson, John & Querstret, 2016) identified the Brief Assessment Checklist for Children (BAC-C; Tarren-Sweeney, 2007) as a potential screening tool for LAC aged 4-11 years. The aim of the current study was to explore the utility and psychometric properties of the BAC-C in a UK LAC population. Design: The study used a mixed-method design. A total of 178 foster/kinship carers completed two questionnaires about a LAC aged 4-11 years: the BAC-C and Strengths and Difficulties Questionnaire (SDQ). Participants were also asked questions about the utility of both questionnaires. Secondly, telephone interviews with five foster carers and two focus groups with professionals working in Child and Adolescent Mental Health Services (CAMHS) were conducted to gather qualitative data about the utility of the BAC-C. Results: The BAC-C total score was significantly correlated with exposure to sexual abuse, a previous referral to CAMHS, SDQ total and subscale scores. The SDQ total scale was the strongest predictor of the BAC-C score, followed by Emotional Problems, Conduct and the remaining SDQ subscales. The factor analysis could not determine a clinically meaningful factor structure. Finally, the thematic analysis revealed three overarching themes regarding the BAC-C: content, format and design and ways of using the information. Conclusion: The BAC-C demonstrated many psychometric strengths in terms of reliability and validity. This was also supported by the qualitative data. However, several limitations of the measure were also revealed and were discussed in the context of mental health services for children.