The aim of this study was to examine the factor structure and psychometric properties of an observer-rated youth alliance measure, the Therapy Process Observational Coding System for Child Psychotherapy-Alliance scale (TPOCS-A). The sample was 52 youth diagnosed with anxiety disorders (M age = 12.43, SD = 2.23, range = 8-15; 56% boys; 98% Caucasian) drawn from a randomized controlled trial. Participants received a manualized individual cognitive behavioral treatment, the FRIENDS for life program, in public community clinics in Norway. Diagnostic status, treatment motivation, and perceived treatment credibility were assessed at pretreatment. Using the TPOCS-A, independent observers rated child-therapist alliance from the third therapy session. Child- and therapist-reported alliance measures were collected from the same session. An exploratory factor analysis supported a one-factor solution, which is consistent with previous studies of self- and observer-rated youth alliance scales. Psychometric analyses supported the interrater reliability, internal consistency, and convergent/divergent validity of the TPOCS-A. Accumulating psychometric evidence indicate that the TPOCS-A has the potential to fill a measurement gap in the youth psychotherapy field. In youth psychotherapy, alliance may be unidimensional, so establishing a strong bond and engaging the child in therapeutic activities may both be instrumental to establishing good alliance early in treatment. However, it is important to be cautious when interpreting the factor analytic findings, because the sample size may have been too small to identify additional factors. Future research can build upon these findings by examining the factor structure of youth alliance measures with larger, more diverse samples.