Sacroiliitis, a condition commonly seen in Ankylosing Spondylitis, is well known to be one of the main pain generators of low back pain, which may result in difficulty with walking. A 20-year old male with history of ankylosing spondylitis presented to the University Hospital of the West Indies, Physical Medicine and Rehabilitation Clinic, with a two-year history of right buttock, low back and groin pain. Radiographic evaluation revealed increased sclerosis and erosive changes in bilateral sacroiliac joints, right greater than left. Right intra-articular sacroiliac joint steroid injection was administered under fluoroscopy guidance. Post-injection visual analogue pain scale (VAS) score with activity improved from 8 to 1 and Oswestry Disability Index improved from 40% moderate disability to 16% minimal disability. The patient’s overall assessment was 95% perceived improvement in pain. This case report illustrates the effectiveness of intra-articular sacroiliac joint steroid injection in treating sacroiliitis in ankylosing spondylitis.