Introduction: Brucellosis remains an important public health problem in many developing countries. This study examines the serum levels of endocan, a novel immune-inflammatory marker, in this potentially difficult to diagnose disease, and their predictive diagnostic value.Methods: Fifty patients under follow-up with diagnoses of brucellosis between May 1, 2020, and December 1, 2020, and 50 healthy individuals constituting the control group were included in the study. Cases were classified as acute, subacute, or chronic, depending on the duration of their symptoms. Patients' plasma specimens were collected before the initiation of brucellosis treatment.Results: Serum endocan levels were higher among the patients with brucellosis than in the healthy control group (p < 0.001). Endocan levels also differed significantly among the patients with acute, subacute, and chronic brucellosis (p < 0.001 for all). Comparison of C-reactive protein (CRP) and the erythrocyte sedimentation rate (ESR) in the patients with acute, subacute, and chronic brucellosis revealed a significant difference only in terms of CRP levels between the acute and chronic patients (p = 0.018). No significant association was observed between serum endocan levels and growth in blood culture or serum agglutination test results in the patients with brucellosis (p > 0.05). However, a significant correlation was found between patients' CRP and ESR values and endocan levels (r = 0.572, and r = 0.415, respectively, p < 0.001). At a cutoff value of 597.35 pg/mL, serum endocan levels exhibited 90% sensitivity and 85% specificity in differentiating patients diagnosed with brucellosis from healthy individuals (area under the curve = 0.927, p < 0.001, 95% confidence interval = 0.877-0.977).Conclusion: Endocan may be a useful guide in differentiating patients with brucellosis from healthy individuals, and in distinguishing between acute, subacute, and chronic brucellosis. Ethics committee approval No: B.30.2.ATA.0.01.00/203.