STUDY DESIGN: Systematic review and meta-analysis. BACKGROUND: Posterolateral fusion (PLF) and posterior lumbar interbody fusion (PLIF) were widely used in the treatment of lumbar isthmic spondylolisthesis (IS). There was a great controversy over the preferred fusion method. OBJECTIVE: The purpose of this study is to evaluate the clinical outcomes between PLF and PLIF for the treatment of IS. MATERIALS AND METHODS: Related studies that compared the clinical effectiveness of PLIF and PLF for the treatment of IS were acquired by a comprehensive search in 4 electronic databases (PubMed, EMBASE, Cochrane Controlled Trial Register, and MEDLINE) from January 1950 through December 2014. Included studies were performed according to eligibility criteria. The main endpoints included: improvement of clinical satisfaction, complication rate, reoperation rate, fusion rate, and reoperation rate. RESULTS: A total of 9 studies were included in the meta-analysis; 6 were low-quality evidence and 2 were high-quality evidence as indicated by the Jadad scale. Compared with PLIF, PLF patients showed lower fusion rates [P=0.005, odds ratio (OR)=0.29 (0.14, 0.58)] and shorter operation times [P<0.00001, weighted mean difference (WMD)=-0.5(-0.61, -0.39)]. No significant difference was found in the term of postoperative visual analogue scale leg score [P=0.92, WMD=0.02 (-0.39, 0.44)] and visual analogue scale back score [P=0.41, WMD=0.20 (-0.28, 0.68)], blood loss [P=0.39, WMD=121.17 (-152.68, 395.01)], complication rate [P=0.42, OR=1.50 (0.56, 4.03)], postoperative Oswestry Disability Index [P=0.3, WMD=1.09 (-0.97, 3.15)], and postoperative clinical satisfaction [P=0.84, OR=1.06 (0.60, 1.86)]. CONCLUSIONS: In conclusion, our meta-analysis suggested that PLF shows significant lower fusion rate compared with PLIF. Although PLIF had more operation time than PLF, there was no significant difference in global assessment of clinical outcome between the 2 fusion procedures. However, future well-designed, randomized-controlled trials are still needed to further confirm our results.