BACKGROUND: Psychologically informed practice emphasizes routine identification of modifiable psychological risk factors being highlighted. OBJECTIVE: The purpose of this study was to test the predictive validity of the STarT Back Screening Tool (SBT) in comparison with single-construct psychological measures for 6-month clinical outcomes. DESIGN: This was an observational, prospective cohort study. METHODS: Patients (n=146) receiving physical therapy for low back pain were administered the SBT and a battery of psychological measures (Fear-Avoidance Beliefs Questionnaire physical activity scale and work scale [FABQ-PA and FABQ-W, respectively], Pain Catastrophizing Scale [PCS], 11-item version of the Tampa Scale of Kinesiophobia [TSK-11], and 9-item Patient Health Questionnaire [PHQ-9]) at initial evaluation and 4 weeks later. Treatment was at the physical therapist's discretion. Clinical outcomes consisted of pain intensity and self-reported disability. Prediction of 6-month clinical outcomes was assessed for intake SBT and psychological measure scores using multiple regression models while controlling for other prognostic variables. In addition, the predictive capabilities of intake to 4-week changes in SBT and psychological measure scores for 6-month clinical outcomes were assessed. RESULTS: Intake pain intensity scores (ß=.39 to .45) and disability scores (ß=.47 to .60) were the strongest predictors in all final regression models, explaining 22% and 24% and 43% and 48% of the variance for the respective clinical outcome at 6 months. Neither SBT nor psychological measure scores improved prediction of 6-month pain intensity. The SBT overall scores (ß=.22) and SBT psychosocial scores (ß=.25) added to the prediction of disability at 6 months. Four-week changes in TSK-11 scores (ß=-.18) were predictive of pain intensity at 6 months. Four-week changes in FABQ-PA scores (ß=-.21), TSK-11 scores (ß=-.20) and SBT overall scores (ß=-.18) were predictive of disability at 6 months. LIMITATIONS: Physical therapy treatment was not standardized or accounted for in the analysis. CONCLUSIONS: Prediction of clinical outcomes by psychology-based measures was dependent upon the clinical outcome domain of interest. Similar to studies from the primary care setting, initial screening with the SBT provided additional prognostic information for 6-month disability and changes in SBT overall scores may provide important clinical decision-making information for treatment monitoring.