Background: Atrial fibrillation (AF) burden is defined as the proportion of time the patient remains in AF over a given period of time; thus, it is theoretically highest in permanent AF and lowest in paroxysmal AF. Inflammation is associated with the initiation and maintenance of AF. However, the relationship between systemic immune-inflammation index (SII) and AF burden is unknown., Objective: In the present study, we investigated the relationship between SII and AF burden., Methods: The present study is a cross-sectional analysis of 453 patients (252 females and 201 males, aged 44 to 94 years) with AF (138 with paroxysmal AF and 315 with permanent AF) who visited the cardiology outpatient clinic between October 2022 and June 2023. SII was calculated as (neutrophils × platelets/lymphocytes). The predictive role of SII and other inflammatory markers in the likelihood of AF pattern was evaluated by logistic regression analyses, and p value < 0.05 was considered statistically significant., Results: Age, diastolic blood pressure, heart rate, diabetes mellitus, neutrophil, platelet-to-lymphocyte ratio, neutrophil-to-lymphocyte ratio, SII, C-reactive protein, red blood cell distribution width, hemoglobin A1c, and left atrial diameter were significantly higher in the permanent AF group. According to the logistic regression analysis, age (p = 0.038), diabetes mellitus (p = 0.024), red blood cell distribution width (p = 0.023), C-reactive protein (p = 0.010), SII (p = 0.001), and left atrial diameter (p < 0.001) significantly contributed to the prediction of the likelihood of permanent AF., Conclusion: SII is independently associated with the AF burden. Prospective studies are needed to determine whether SII may be useful in identifying patients at high risk for AF progression.