The study investigated whether the use of carbon fiber-reinforced PEEK screw material (CF-PEEK) can reduce magnetic resonance imaging (MRI) artifact formation. Two consecutive groups of patients were treated for degenerative spinal disorders of the lumbar spine with dorsal transpedicular spinal fusion. The first group (n = 27) received titanium pedicle screws. The second group (n = 20) received CF-PEEK screws. All patients underwent an MRI assessment within the first four postoperative weeks. For each operated segment, the surface of the artifact-free vertebral body area was calculated as percentage of the total vertebral body. For each implanted segment, the assessability of the spinal canal, the neuroforamina, and the pedicle screws, as well as the surrounding bony and soft-tissue structures was graded from 1 to 5. A mean artifact-free vertebral body area of 48.3 ± 5.0% was found in the in the titanium group and of 67.1 ± 5.6% in the CF-PEEK group (p ≤ 0.01). Assessability of the lumbar spine was significantly improved for CF-PEEK screws (p ≤ 0.01) for all measurements. CF-PEEK pedicle screws exhibit smaller artifact areas on vertebral body surfaces and their surrounding tissues, which improves the radiographic assessability. Hence, CF-PEEK may provide a diagnostic benefit.