The purpose of this research was to evaluate the efficacy of transforaminal lumbar interbody fusion (TLIF) against circumferential fusion for the treatment of adult based on radiographic and patient-reported outcome measures (PROMs) isthmic spondylolisthesis (IS). Adults with IS often require decompression and fusion for definitive treatment. Although several different fusion methods have been documented, research into determining which method is best is lacking. Patients with IS who underwent a 1-year or longer follow-up after undergoing a 1- or 2-level circumferential fusion or TLIF were considered. Data on patient demographics, surgical procedures, and PROMs were culled from the patients’ electronic medical records. Results were compared using multivariate regression analysis and descriptive statistics, with a P less than 0.05 indicating statistical significance. There were a total of 78 fusions performed, including 50 TLIF and 48 open decompression and fusions and 30 posterior percutaneous instrumentation fusions. When comparing circumferential procedures (3.56±0.96 d) versus TLIFs (2.88±1.14 d) (P=0.002) the latter resulted in a substantially longer length of stay (P=0.002). Segmental lordosis was improved more in the circumferential fusion group after surgery [anterior/posterior (A/P): 6.45, TLIF: −1.99, P<0.001], posterior disk height (A/P: 12.6 mm, TLIF: 8.9 mm, P<0.001), and ∆disk height (A/P: 7.7 mm, TLIF: 3.6 mm, P<0.001). All patient-reported outcome measures (PROMs) revealed statistically significant increases in both groups (P<0.001). Despite a greater prevalence of perioperative surgical problems in the circumferential fusion group (12.82% vs. 2.00%, P=0.049), there was no difference in the rates of 30-day readmissions (P=0.520) or revision operations in which (P=0.057). Although radiographic outcomes are better after a circumferential fusion than after a TLIF, the lengthier hospital stay and higher risk for perioperative problems come at a cost. There were no significant variations in PROMs or readmissions or revisions after surgery based on the method used.