Despite increasing pressure to use evidence-based practice, including standardized assessment, most empirically supported assessment tools are difficult to use in clinical practice. To facilitate mental health clinicians’ ability to incorporate psychometrically sound measurement into their treatment of childhood anxiety disorders, we sought to demonstrate the utility of a simple anxiety rating procedure. This procedure was enacted through the use of a single-item child Anxiety Severity Rating (ASR), which was examined within a clinical sample of 324 youths ranging from 7–17 years of age. Results indicate that this basic rating procedure demonstrates interrater reliability, convergent and divergent validity, relative utility in comparison to a commonly used rating scale, correspondence to ratings often used in research settings, and sensitivity to change with treatment. Given the properties of such data, applying simple rating procedures such as the ASR may represent a convenient means to achieving an initial step toward implementing evidence-based assessment in clinical practice within a variety of settings. The current study provides clinicians with the materials to implement the ASR in practice and documentation of the ASR’s validity.