Background: Despite numerous reports on mini-open transforaminal lumbar interbody fusion (TLIF), there exists a few studies to compare directly mini-open TLIF and conventional-open TLIF procedures. This study evaluated the usefulness and safety of mini-open TLIF for degenerative lumbar diseases and instabilities. Material and methods: Sixty-eight patients underwent TLIF with pedicle screw fixation for degenerative disc disease or spondylolisthesis with more than 12 months follow-up; 22 patients underwent mini-open TLIF and 46 patients underwent conventional-open TLIF. Data of incision, perioperative parameters, complications, fusion rate, and clinical data were reviewed. Results: The length of incision was shorter in mini-open TLIF group (p=0.04), but satisfaction rate of incision was not statistically different (p=0.18). The VAS and mODI were significant lower in mini-open TLIF (p=0.037, 0.031, respectively) at postoperative 7 days. Less estimated blood loss and less change in hemoglobin and blood pressure during operation was observed in mini-open TLIF group than conventional-open TLIF group. The fusion rate was also not statistically different. The complication including the pedicle screw fracture, bony spur, adjacent level instability was observed in 14% in the mini-open TLIF group and 10% in the conventional-open TLIF group (p=0.63). Conclusion: The mini-open TLIF with pedicle screw fixation provides excellent clinical results and may be an operation of choice for lumbar spinal fusion. The long-term clinical, functional and radiological results were similar in the mini-open and conventional-open TLIF. But, the mini-open TLIF is a viable alternative to the conventional-open TLIF with advantage of lesser blood loss, less change of hemoglobin and blood pressure, shorter incision, and lesser postoperative pain.