The goal of this study is to evaluate the effect of adding dexmedetomidine as an adjuvant to steroid injection versus steroid alone in chronic low back pain caused by sacroiliac joint arthritis. Sixty patients of both sex, ASA grade 1 and 2, between the ages of 18-70 years, BMI less than 30 kg/m2, after diagnosis of sacroiliac joint dysfunction and failure of conservative management were randomly allocated into two groups (n=30). Group (1): patients received SI injection with 2ml of long-acting corticosteroid (14 mg Betamethasone) and 0.5 ml of normal saline and group (2): patients received SI injection with 2ml of long-acting corticosteroid (14 mg Betamethasone) and 0.5ml dexmedetomidine (50 mcg). Patients were observed for vital signs, pain intensity and possible side effects in the recovery room for 4 hours then discharged. The patient's pain intensity using Numerical Rating Scale, or functional improvement using Oswestry Disability Index and Functional Rating Scale and complications were followed up at 2 weeks, 4 weeks and 12 weeks. While, short assessment of patient satisfaction was assessed 2 weeks after injection. The results revealed that addition of dexmedetomidine to steroids in sacroiliac joint injection is of low value. There was no statistically significant difference between the steroid group and the dexmedetomidine group regarding the changes in the NRS, ODI and FRI scores at 2 weeks, 4 weeks and 12 weeks after injection.