Background data: The order of steps for lumbar spine pedicle screw fixation (PSF) and posterior lumbar interbody fusion (PLIF) may differ from one surgeon to another, which may affect the surgical outcomes. Purpose: To evaluate the difference between PSF before and after PLIF in patients with degenerative lumbar spine diseases. Study design: A comparative retrospective clinical study. Patients and methods: This study reported patients who underwent lumbar PSF and PLIF from January 2018 to March 2023. The patients were allocated into two groups: group A (PSF before PLIF) and group B (PSF after PLIF). A total of 567 patients, 264 in group A and 303 in group B, were recruited for this study. Outcome parameters included operative time, operative blood loss, operative blood transfusion, and operative complications. Results: No significant differences were found between the two groups when comparing surgical time and intraoperative complications (P > 0.05). However, compared with group B, a significant decrease was found in intraoperative blood loss and the need for intraoperative blood transfusion in group A (P < 0.05). Conclusion: This study suggests that the lumbar PSF is preferred before rather than after PLIF as it significantly reduces operative blood loss and the need for blood transfusion.