--- - |2+ Background Given the relatively high prevalence of anxiety problems among young people and their adverse consequences if left untreated, it is important that clinicians and researchers have access to reliable and valid assessment tools to facilitate early detection, case formulation, treatment design and evaluation of outcomes. Method This paper presents the findings of a pragmatic review of the literature regarding the assessment of anxiety in young people in multiple contexts, including mental health services, school‐based screening and research trials. Results Commonly used diagnostic interviews, questionnaire measures and alternative assessment methods are described, along with psychometric properties and practical issues. The review indicates the complexities of assessing anxiety problems given the high level of comorbidity between anxiety disorders and with depression. It also highlights the different approaches required for assessment across different age groups, the need for multiple informants and issues relating to the lack of agreement between reporters. There is a strong evidence‐base for several diagnostic instruments and anxiety scales, although the accuracy of youth and parent report scales in forming clinical diagnoses is not sufficiently strong to justify their use in isolation for diagnostic purposes. Conclusions The assessment of youth anxiety should ideally include a multiinformant, multimethod approach, with measures tailored to the age of the child, and the purpose of the evaluation. There is now a sufficiently strong research base to enable clinicians and researchers to ensure that they select evidence‐based instruments. - Child and Adolescent Mental Health, Volume 23, Issue 3, Page 266-282, September 2018.