One hundred fifty eight patients with symptomatic single-level (degenerative, isthmic, or iatrogenic) spondylolisthesis were randomized 1:1 to Transforaminal Lumbar Interbody Fusion (TLIF) (n=78) or Posterior Lumbar Interbody Fusion (PLIF) (n=80). The primary outcome was change in ODI from baseline to 12 months. Secondary outcomes included QALYs (EQ-5D-5L, SF-36), back/leg pain (NRS), anxiety/depression (HADS), peri-operative blood loss, operative time, length of stay, and complications. Outcomes were assessed pre-op and at 3, 6, and 12 months. Overall, the results showed non-inferiority of TLIF vs PLIF for ODI and broadly similar secondary outcomes; SF-36–derived QALYs favored TLIF statistically but without clinical importance. These findings suggest TLIF and PLIF yield comparable 1-year patient-reported outcomes and peri-operative profiles.