PURPOSE: To find the cut-off values in the Myelopathy Disability Index (MDI) that will allow us to classify the severity of Degenerative Cervical Myelopathy (DCM) into mild, moderate and severe. METHODS: Cross-sectional study with prospective data collection, with a total of 64 patients diagnosed with Degenerative Cervical Myelopathy (DCM). Anthropometric, diagnostic, neurological, functional and quality of life variables were collected. A Receiver Operating Curve (ROC) was performed. The cut-off points were validated by comparing the functional status of patients in the 3 groups and their Nurick scores. RESULTS: Sixty-four patients (23 women) with a mean age of 61.97 (SD 11.57) participated in this study. The majority of patients were Nurick I (28.13%) and Nurick II (32.81%). The medium MDI was 7.36 (SD 6.66) and the mJOA was 14.08 (SD 2.57). The mild-moderate cut-off value was between 4 and 5, with an Area Under the Curve (AUC) of 0.805, sensitivity of 0.853 and specificity of 0.6. For moderate-severe, the cut-off value obtained was between 7 and 8, with an AUC of 0.862, sensitivity of 0.857 and specificity of 0.684. Patients with greater severity had significantly lower functionality, with a P-value of 0.004 in the 30 Metre Walking Test and 0.005 in the Nine-Hole Peg Test. Established severity groups were also significantly related to the different categories of the Nurick score (P-value = 0.000). CONCLUSION: MDI values between 0 and 4 correspond to mild DCM, between 5 and 7 would be moderate DCM and from 8 to 30 indicate severe DCM.