Background: Acupuncture is considered a clinically effective and cost-effective treatment option for chronic low back pain. However, few clinical trials have evaluated the dose dependence of acupuncture for chronic low back pain based on the number of sessions. Conclusions are conflicting and there is little high-quality evidence to support the cumulative effects of repeated interventions. A randomized controlled trial to investigate the optimal number of sessions of acupuncture in addition to usual care for adults with chronic low back pain is required; a feasibility study to test the rationale and method for the full-scale trial is the first step in that process. Design: A pragmatic parallel three-armed randomized, controlled feasibility study. Methods: Forty-five participants with chronic low back pain will be recruited locally and randomized on a 1:1:1 basis to receive usual care plus 4 (n = 15), 7 (n = 15) or 10 sessions (n = 15) of semi-standardized acupuncture. Primary outcomes are acceptability of and adherence to different numbers of sessions of acupuncture, as well as the feasibility of the recruitment approach and completion of the specific outcome measures. Secondary outcomes include pain intensity and patient satisfaction. Follow-up questionnaires will be collected at discharge, 6, and 12 weeks after randomization. Discussion: Outcomes will inform the decision to conduct a full-scale trial to definitively test the dose dependence of acupuncture. Findings will add to the limited evidence available regarding the optimal number of sessions of acupuncture in the management of chronic low back pain, as well as being clinically relevant to clinicians, researchers and policy makers.