Background: degenerative lumbar disorders affect millions of people causing low back pain, which can restrict mobility and daily activities. Lumbar fusion operations are used as a treatment of degenerative lumbar disorders. However, the better choice among fusion techniques is still controversial. Objective: to compare the clinical and radiological outcome of Transforaminal Lumbar Interbody Fusion (TLIF) and Posterolateral fusion (PLF) in the treatment of degenerative lumbar spine stenosis and degenerative spondylolisthesis. Patients and Methods: a prospective study was conducted on 40 patients with degenerative lumbar spondylolisthesis and degenerative lumbar spine stenosis. Twenty patients underwent transforaminal lumbar interbody fusion and 20 patients underwent posterolateral fusion. Patients were followed up using the visual analogue scale (VAS) for back and leg pain and Oswestry Disability Index (ODI). Final fusion assessment was done according to Bridwell criteria. Results: ODI and VAS of leg and back pain improved in the two groups with no significant differences between the two groups whether after six or twelve months of follow up. TLIF group shows a high grade of fusion according to Bridwell grading criteria for spinal fusion and significantly better than the PLF group of patients either in six-month follow up (p=0.045) or twelve-month follow up (p=0.04). Conclusion: both TLIF and PLF provide improvement of disability and pain in patients with degenerative lumbar disorders. TLIF is superior to PLF with regard to achieving radiographic fusion. There is no significant clinical or functional outcome to support the use of TLIF over PLF in the treatment of degenerative lumbar disorders.