A 19-year-old woman sustained a vertical shear type pelvic fracture. Sacroiliac fixation using computed tomography (CT)-guided cannulated screws was performed for a left sacroiliac dislocation fracture, and a satisfactory result was obtained over time. Patients who have posterior instability of the lateral compression or vertical shear type do not obtain adequate stability by fixation of the anterior part alone; and they often have persistent residual pain, necessitating internal fixation of the posterior part later. Advantages of CT-guided sacroiliac screw fixation include precise evaluation of the degree of reduction and absence of nerve and vascular damage during the time the screw is inserted into the sacral body. This procedure is a useful, safe method owing to its minimal invasiveness in patients with unstable pelvic fractures that are reducible by manual manipulation or traction.