Objective <p>To explore the manifestations of extradural fat in patients with Redundant nerve roots (RNRs) via lumbar MRI.</p> Methods <p>A total of 492 patients with RNRs were enrolled and divided into two groups: Group A (<i>n</i> = 459) with known potential causes of RNRs, such as lumbar spondylolisthesis, scoliosis, disc herniation, and ligamentum flavum hypertrophy; Group B (<i>n</i> = 33) without the aforementioned causes; and control Group C (<i>n</i> = 33) with age- and sex-matched RNRs-negative patients. MRI was used to assess the morphology of extradural fat and the appearance of the cauda equina and to measure the subcutaneous fat thickness in the lumbar-sacral region (LSFTT). Statistical analysis was performed via t tests, chi-square tests, and Wilcoxon signed-rank tests, with <i>p</i> &lt; 0.05 considered statistically significant.</p> Results <p>In Group A, there was no statistically significant difference in the LSFTT among the different grades of extradural fat. In Group B, the incidence rates of Grade 2 and Grade 3 extradural fat were 66.7% and 24.2%, respectively, which were significantly greater than the 27.3% and 0% reported in Group C, with a statistically significant difference between Groups B and C (<i>p</i> &lt; 0.001). The correlation coefficient between increased extradural fat and RNRs was 0.669 (<i>p</i> &lt; 0.001). There were no statistically significant differences in the morphology or relative length of the RNRs among the different grades of extradural fat in Group B.</p> Conclusion <p>MRI is an important tool for assessing extradural fat and RNRs, providing crucial information for clinical decision-making and improving patients’ prognoses. Increased extradural fat may contribute to the development of RNRs and should be a concern for clinicians.</p>