To date, interventions for childhood social phobia have examined outcome primarily in terms of symptomatic reduction or efficacy. Although more emphasis is being placed on reporting clinically relevant outcome, few studies have provided a systematic assessment of treatment effectiveness, perhaps due to a lack of an appropriate assessment inventory. The current study presents the initial psychometric characteristics of the Child Social Functioning Inventory (CSFI), a self-report inventory designed to assess social functioning of preadolescent children. The CSFI contains 24 items with a 6-factor structure. The results indicate that the CSFI has good internal consistency and adequate test-retest reliability. In addition, assessment of the construct validity, including concurrent, convergent, and discriminant validity suggest that the CSFI is a valid inventory of social functioning for children ages 10 or above. Implications for assessment and treatment outcome are discussed.