Background: Diabetic Foot Ulcer (DFU) is a common and challenging complication of diabetes mellitus, associated with high recurrence, hospitalization, disability, and mortality rates. The Systemic Immune Inflammatory Index (SIRI) based on complete blood counts has been shown to correlate with several diseases but has not been widely studied in DFU.This study aimed to explore the relationship between SIRI and the presence of DFU in individuals with diabetes using data from the National Health and Nutrition Examination Survey (NHANES). Methods: A cross-sectional analysis was conducted on 1246 individuals with diabetes from NHANES cycles 1999-2000, 2001-2002, and 2003-2004. DFUs were identified through patient self-reported data. Multivariate logistic regression models assessed the association between SIRI and DFU, adjusting for potential confounders. Subgroup and interaction analyses were also performed. Results: A total of 117 patients were identified as having DFU. Elevated SIRI levels were significantly associated with DFU presence. In fully adjusted models, a 1-unit increase in SIRI was associated with 24.0% higher odds of DFU prevalence (OR = 1.24; 95% CI: 1.07, 1.43) Subgroup analyses revealed consistent associations across different groups of age, gender, body mass index (BMI), HbA1c, blood glucose, and hemoglobin levels. Conclusion: The findings indicate a positive correlation between SIRI and DFUpresence. Further research is warranted to elucidate the mechanistic links and explore the clinical utility of SIRI in DFU management.