Cervical intradural extramedullary tumors (IDEMTs) are generally benign lesions that can cause neurological impairment by compressing the spinal cord. Although tumor occupancy ratio within the spinal canal has been reported to be associated with symptoms and postoperative outcomes, patients with similar occupancy ratios may show different neurological status and recovery. This suggests that tumor size alone may not fully explain functional outcomes. Shape factor (SF) is a quantitative MRI- based index of spinal cord morphology, but its clinical significance in cervical IDEMTs remains unclear. This study investigated whether SF is associated with postoperative functional recovery after surgery for cervical IDEMTs. We retrospectively reviewed 35 patients with benign cervical IDEMTs who underwent surgery at our institution between January 2011 and December 2024 and were followed for at least 1 year. Neurological function was evaluated using the cervical Japanese Orthopaedic Association (JOA) score preoperatively and at 1 year postoperatively. Because most patients achieved clinically meaningful improvement, patients were divided according to whether they achieved a full JOA score of 17 points at 1 year. MRI parameters included tumor occupancy ratio, spinal cord occupancy ratio, and SF at the level of maximal compression. Cervical alignment, C2–7 range of motion, local segmental range of motion, and flexion-extension slip distance were also assessed. The mean JOA score improved from 12.8 ± 2.67 preoperatively to 16.3 ± 1.02 at 1 year. Full recovery was achieved in 19 patients. Dynamic radiographic parameters did not differ between groups. Among MRI parameters, SF was significantly higher in the full-score group. Multivariable logistic regression analysis showed that SF was an independent predictor of achieving a full JOA score at 1 year, with an odds ratio of 2.06 per 0.1 increase. The area under the receiver operating characteristic curve was 0.697, with a cutoff value of 0.568. SF was independently associated with achieving a full JOA score after surgery for cervical IDEMTs. Assessment of spinal cord morphology may provide additional prognostic information beyond conventional compression-based indices.