Background: Management of chronic sacroiliac joint (SIJ) pain among patients who do not respond to nonsurgical treatment is increasingly turning toward minimally invasive SIJ fusion. There are different techniques available to perform this procedure, with the lateral technique being more commonly studied than the posterior oblique technique. This study examined the effects of these techniques on pain relief and functional improvement, both preoperatively and at a 12-month follow-up. Methods: This retrospective cohort study analyzed data from 45 patients who underwent SIJ fusion. Included patients were ≥50 years old, nonresponsive to conservative treatment. Subjects were divided into 2 cohorts based on the SIJ fusion technique. Primary outcomes were pain relief, measured by Visual Analog Scale (VAS), and functional improvement, determined by the Oswestry Disability Index (ODI); both were recorded and assessed at baseline, postoperative, and the change from pre- to postoperative. Additionally, data regarding patient demographics, previous lumbar fusion, operative time, and duration of hospital stay were collected and analyzed. Results: Baseline demographic and clinical variables exhibited no significant differences in distribution between groups. The posterior oblique cohort demonstrated a substantial reduction in operative time (over 50%) and duration of hospital stay compared to lateral cohort. Pain relief (postoperative VAS: lateral 3.5±1.7 vs. posterior oblique 2.4±1.5 [p=.02]) and functional improvement (postoperative ODI: lateral 29.6±7.3 vs. posterior oblique 21±5.7 [p≤.001]) were significantly better in the posterior oblique group. Pre- to postoperative improvement analysis indicated greater reduction in pain (VAS: lateral -4.4±1.9 vs. posterior oblique -6.1±1.5 [p=.002]) in the posterior oblique group. Conclusions: Compared to the lateral technique group, patients undergoing minimally invasive SIJ fusion through the posterior oblique technique experienced greater pain relief and demonstrated a trend toward better functional improvement, with shorter operative times and duration of hospital stay. The posterior oblique technique may be more efficient and beneficial to manage patients suffering from chronic SIJ pain through joint fusion.