Objective:To evaluate the effectiveness of traction in improving low back pain, functional outcome, and disk morphology in patients with herniated intervertebral disks.Data Source:PubMed, Scopus, Embase, and the Cochrane Library were searched from the earliest record to July 2019.Review methods:We included randomized control trials which (1) involved adult patients with low back pain associated with herniated disk confirmed by magnetic resonance imaging or computed tomography, (2) compared lumbar traction to sham or no traction, and (3) provided quantitative measurements of pain and function before and after intervention. Methodological quality was assessed using the physiotherapy evidence database (PEDro) scale and Cochrane risk of bias assessment.Results:Initial searches for literature yielded 3015 non-duplicated records. After exclusion based on the title, abstract, and full-text review, 7 articles involving 403 participants were included for quantitative analysis. Compared with the control group, the participants in the traction group showed significantly greater improvements in pain and function in the short term, with standard mean differences of 0.44 (95% confidence interval (CI): 0.11–0.77) and 0.42 (95% CI: 0.08–0.76), respectively. The standard mean differences were not significant to support the long-term effects on pain and function, nor the effects on herniated disk size.Conclusion:Compared with sham or no traction, lumbar traction exhibited significantly more pain reduction and functional improvements in the short term, but not in the long term. There is insufficient evidence to support the effect of lumbar traction on herniated disk size reduction.