Introduction: Atrial fibrillation (AF) is the most common form of sustained cardiac arrhythmia, characterized by irregular R–R intervals and the absence of distinct P waves with irregular atrial activity (also known as fibrillatory waves). C-reactive protein (CRP), a marker of systemic inflammation, has been implicated in various cardiovascular diseases, including AF. Neutrophil-to-lymphocyte ratio (NLR) reflects the balance between innate and adaptive immunity and has emerged as a potential prognostic marker in cardiovascular conditions. Despite extensive research on AF, the existing literature predominantly focuses on individuals of white ethnicity. Therefore, further investigation is needed, particularly in diverse ethnic populations. To address this gap, this study utilized a Korean hospital database to explore the relationship between AF and two inflammatory markers: CRP and NLR. Methods: A retrospective cohort study was conducted on 164 patients, equally divided between AF and NSR groups. CRP levels and NLR were measured using standard assays, and ECG data confirmed AF diagnosis. Statistical analysis, including ROC cuve evaluation, was performed to assess the discriminatory power of these biomarkers. Results: Analysis of the study data revealed a significant difference in CRP levels between AF patients and those with normal sinus rhythm, indicating a pronounced inflammatory response associated with AF. However, NLR did not exhibit a substantial difference between the two groups. Conclusion: CRP may serve as a reliable biomarker for detecting inflammation in patients with AF, whereas NLR may not be as discriminatory in this patient population.