Abstract Objective To develop a systematic approach for magnetic resonance imaging (MRI) analysis, imaging spectrum, and classification system for the staging of post-COVID-19 head and neck mucormycosis. Method The study included 63 post-COVID-19 patients with pathologically proven mucormycosis who underwent head and neck MR imaging. Three independent radiologists assessed the imaging spectrum of mucormycosis, MRI characteristics of sino-nasal mucormycosis, and extra-sinus extension, and submitted a final staging using a systematic approach and a proposed categorization system. A consensus reading was considered the reference imaging standard. The kappa statistics were used to assess the categorization system's diagnostic reliability. Results The overall interreader agreement of the MR staging system was very good (k-score = 0.817). MR imaging spectrum involved localized sino-nasal mucormycosis (n = 7 patients, 11.1%), sino-nasal mucormycosis with maxillo-facial soft tissue extension (n = 28 patients, 44.5 %), sino-nasal mucormycosis with maxillo-facial bony extension (n = 7 patients, 11.1%), sino-naso-orbital mucormycosis (n = 13 patients, 20.6%), and sino-nasal mucormycosis with cranium or intracranial extension (n = 8 patients, 12.7%). Extra-sinus extension to the orbit and brain did not have significant association with involvement of the posterior ethmoid/sphenoid sinuses and maxillo-facial regions (p > 0.05). MRI-based staging involved four stages: stage 1 (n = 7, 11.1%); stage 2 (n = 35, 55.6%), and stage 3 (n = 13, 20.6%), and stage 4 (n = 8, 12.7%). Involvement of the bone and MR-based staging were significant predictors of patients’ mortality p = 0.012 and 0.033, respectively. Conclusion This study used a diagnostic-reliable staging method to define the imaging spectrum of post-COVID-19 head and neck mucormycosis and identify risk variables for extra-sinus extension.