Background. About 85% of the patients with low back pain seeking medical care have nonspecific low back pain (NsLBP), implying that no definitive cause can be identified. Many pain conditions are linked with elevated serum levels of (pro-)inflammatory biomarkers. Purpose. To unravel the etiology and get better insight in the prognosis of NsLBP, the aim of this study was to assess the association between (pro-)inflammatory biomarkers and the presence and severity of NsLBP. Methods. A systematic literature search was made in Embase, Medline, Cinahl, Web-of-science, and Google scholar up to January 19th 2017. Included were studies reporting on patients >18 years with NsLBP, in which one or more pro-inflammatory biomarkers were measured in blood plasma. The methodological quality of the included studies was assessed using the Newcastle Ottawa Scale (NOS). A best-evidence synthesis was used to summarize the results from the individual studies. Results. Included were 10 studies which assessed 4 different (pro-)inflammatory biomarkers. For the association between the presence of NsLBP and C-reactive protein (CRP), interleukin 6 (IL-6) and tumor necrosis factor (TNF)-α limited, conflicting and moderate evidence, respectively, was found. For the association between the severity of NsLBP and CRP and IL-6, moderate evidence was found. For the association between the severity of NsLBP and TNF-α and RANTES conflicting and limited evidence, respectively, was found. Conclusions. This study found moderate evidence for i) a positive association between the (pro-)inflammatory biomarkers CRP and IL-6 and the severity of NsLBP, and ii) a positive association between TNF-α and the presence of NsLBP. No conflicts of interest. No funding obtained