This paper presents the psychometric evaluation of brief measures of therapeutic alliance (TA) for youths, clinicians and caregivers and a longitudinal analysis of relationships between changes in TA and changes in youth symptom and functioning severity. Psychometric analyses using methods from Classical Test Theory, Item Response Theory, and Factor Analysis indicate that the measures of TA used in this study offer something new for both practice and research. The measures have variability, sensitivity to change over time, brevity and can be used with multiple parties through parallel forms. The longitudinal analyses, employing hierarchical linear modeling with time-varying covariates, found that TA ratings of the clinician correlated with symptom improvement as rated by the clinician, caregiver and youth. Additional analyses showed that decreases in clinician-rated youth TA was most important in predicting a lower rate of youth improvement. Implications for future research and clinical practice are discussed.