Background: Red cell distribution width (RDW), a measure of erythrocyte size variation, has been implicated as a potential biomarker in various malignancies. However, its role in distinguishing between benign and malignant endometrial diseases remains unclear. This study aimed to evaluate the diagnostic utility of RDW and its correlation with disease severity in endometrial carcinoma. Methods: This cross-sectional study included 183 women diagnosed with either benign or malignant endometrial diseases. RDW levels were measured and analyzed for their diagnostic significance. Statistical analysis included independent t-tests to compare RDW values between groups and ROC analysis to determine diagnostic accuracy. Correlation between RDW and FIGO staging was also evaluated. Results: RDW was significantly higher in the malignant group (46.64±6.18) compared to the benign group (43.05±7.03; p < 0.001). A non-significant positive correlation was observed between RDW and FIGO staging (r = 0.031, p = 0.815). The ROC analysis yielded an area under the curve (AUC) of 0.463 (95% CI: 0.374–0.552; p = 0.414). The best cutoff value for RDW was 49.50, with a sensitivity of 17% and specificity of 90%. Conclusion: While elevated RDW is associated with endometrial malignancy, its diagnostic accuracy is limited. However, RDW may serve as a supplementary marker when combined with other diagnostic tools, particularly in low-resource settings. Further studies with larger cohorts are needed to validate these findings and explore RDW’s prognostic value.