Study Design: Retrospective study. Objectives: Giant cell tumors (GCTs) of the mobile spine can be locally aggressive. This study described and classified the typical and atypical appearance of aggressive spinal GCTs according to imaging findings to help the imaging diagnosis, especially for patients with rapid neurological deficit that may require emergent surgery without biopsy. Methods: Computed tomography (CT) and magnetic resonance imaging (MRI) scans of patients diagnosed with aggressive spinal GCTs at single center were reviewed. Results: Overall, 101 patients with 100 CT images and 94 MR images were examined. All lesions were osteolytic with cortical destruction; 95 lesions showed epidural extension; 90 were centered in the vertebral body; 82 showed pathological fracture and/or collapse of the vertebral body; 78 had pseudotrabeculation on CT; 80 showed low-to-iso signal intensity or heterogeneous high-signal intensity with cystic areas on the T2-weighted images; 9 showed fluid–fluid level on T2-weighted images; and 61 patients showed marked enhancement on contrast-enhanced CT and/or MRI. Forty-one lesions (40.6%) had at least 1 atypical radiographic feature: 19 involved ≥2 segments; 11 were centered in the posterior neural arch; 10 had a paravertebral mass over 2 segments; 16 showed partial margin sclerosis with partial cortical destruction on CT scans; and 3 showed mineralization within the tumor on CT. Eighty-eight patients underwent CT-guided biopsy with a diagnostic accuracy rate of 94.3%. Conclusions: Spinal GCTs might appear more radiologically atypical, and about 40% of the lesions may have at least 1 atypical feature. CT-guided biopsies are recommended for definitive diagnosis.