This study examined the effectiveness of a modified cognitive-behavioral therapy (CBT) program for the treatment of a cognitively delayed 8-year-old girl presenting with social phobia, selective mutism, and generalized anxiety disorder (GAD). Multimethod assessment, at pretreatment and posttreatment, included a semistructured diagnostic interview, self-reports, and parent and teacher reports. Cognitive delays were apparent at the initial assessment and confirmed on review of previous evaluations. CBT for anxious youth was implemented in a modified fashion to ensure that the methods built on the child’s competencies and were compatible with her developmental capacities. Following 20 CBT sessions, posttreatment assessment indicated significant reduction in anxiety symptoms, as indicated by the diagnostic interview and self-report and other report of symptomatology. The child no longer met diagnostic criteria for GAD or selective mutism at posttreatment. The case study illustrates how CBT can be modified and applied flexibly in response to individual needs and limitations of the child.