10 studies including 5 randomized controlled trials (RCTs) and 5 prospective trials were included in this meta-analysis to compare the safety and effectiveness of interspinous spacers and posterior lumbar interbody fusion (PLIF) in the treatment of patients with degenerative lumbar spinal diseases. Findings indicated no significant differences between treatment groups for pooled complication rates, postoperative pain, postoperative disability, duration of hospital stay, and postoperative range of motion in the distal segment. A significantly lower estimated blood loss, shorter operative time, and significantly larger postoperative range of motion at the surgical segment, but a smaller range of motion at the proximal segment was reported in the interspinous spacer group compared to the PLIF group. The results of this meta-analysis should be interpreted with caution as a large proportion of the studies included were not RCTs. Additional RCTs of higher quality should be conducted to include larger sample sizes, longer follow-up periods, and a cost-effectiveness analysis in order to verify the present findings.