ObjectivesRunning is one of the most accessible forms of exercise, yet its suitability for adults with chronic low back pain (LBP) is unknown. This study assessed the efficacy and acceptability of running in adults with chronic LBP.MethodsThis two-arm parallel (1:1) individually randomised controlled trial allocated 40 participants (mean (SD) age: 33 (6) years, female: 50%) with non-specific chronic LBP to a 12-week intervention or waitlist control. The intervention was a progressive run–walk interval programme comprising three 30-min sessions per week that were digitally delivered and remotely supported by an exercise physiologist. Efficacy outcomes were self-reported pain intensity (100-point visual analogue scale) and disability (Oswestry Disability Index). Acceptability outcomes were attrition, adherence and adverse events.ResultsAt 12-week follow-up, the intervention improved average pain intensity (mean net difference (95% CI): −15.30 (–25.33, –5.27) points, p=0.003), current pain intensity (−19.35 (–32.01, –6.69) points, p=0.003) and disability (−5.20 (–10.12, –0.24) points, P=0.038), compared with control. There was no attrition, and mean (SD) training adherence was 70% (20%; ie, 2.1 of 3 sessions per week). Nine non-serious adverse events deemed likely study-related were reported (lower limb injury/pain: n=7, syncope associated with an underlying condition: n=1, LBP: n=1).ConclusionsA run–walk programme was considered an acceptable intervention by the participants to improve the pain intensity and disability in individuals aged 18–45 years with non-specific chronic LBP when compared with the control. An individualised and conservative run–walk programme should be considered a suitable form of physical activity for adults with chronic LBP.Trial registration numberAustralian New Zealand Clinical Trials Registry: ACTRN12622001276741. Registered on 29 September 2022.