Purposes of the study and background. Cognitive Functional Therapy (CFT) is a psychologically informed, physiotherapist-led intervention that targets the biopsychosocial complexity of persistent low back pain (LBP). CFT has demonstrated positive outcomes in two randomised controlled trials (RCT) but has not previously been evaluated in the United Kingdom National Health Service (NHS). This study aimed to determine the feasibility of completing a definitive RCT, that will evaluate the clinical and cost-effectiveness of CFT in comparison to usual physiotherapy care (UPC) for people with persistent LBP in the NHS. Methods and results. A two-arm parallel feasibility RCT compared CFT with UPC in participants with persistent LBP. Data concerning study processes, resources, management and patient reported outcome measures (disability, pain intensity, quality of life and psychosocial function) were collected at baseline, three and six-month follow-up, analysed and evaluated in order to establish feasibility. Sixty participants (n=30 CFT and n=30 UPC) were recruited with 71.6% (n=43) retained at six-month follow-up. CFT was delivered to fidelity, relevant and clinically important outcome data were rigorously collected and CFT was tolerated by participants with no safety concerns. The Roland-Morris disability questionnaire was the most suitable primary outcome measure and sample size calculations were completed for a definitive RCT. Intention to treat analysis indicated a signal of effect in favour of CFT with moderate and large between group effect sizes observed across outcome measures at six-month follow-up. Conclusion. It is feasible to conduct a randomised study of CFT in comparison to UPC for NHS patients. A future fully powered clinical and cost effectiveness RCT could be completed. Conflicts of interest: No conflicts of interest. Sources of funding: Chartered Society of Physiotherapy, Physiotherapy Research Foundation