Angiogenic T (Tang) cells and endothelial progenitor cells (EPCs) play a role in maintaining vascular integrity and repair. This study considers the association between them and Behçet disease (BD) and disease activity. Fifty patients with BD and forty-five age- and gender-matched healthy controls were included in the study. The participants’ demographic, clinical, and laboratory characteristics were recorded, and their blood Tang cell and EPC counts were determined. Fifty patients were diagnosed with BD, consisting of 24 females and 26 males. The blood Tang cell (3.5 ± 1.2 cells/μL in patients, 4 ± 0.9 cells/μL in controls,p= 0.046)) and EPC (2.9 ± 0.9 cells/μL in patients, 3.7 ± 1 cells/μL in controls,p= 0.001) counts were significantly lower for the patient group with BD than for the control group. The blood Tang cell (42.5 ± 4.9% in active patients, 48.9 ± 7.9% in inactive patients,p= 0.001) and EPC (35.5 ± 6.4% in active patients, 41.2 ± 6.3% in inactive patients,p= 0.004) levels were lower for the patient group with active BD than for the inactive patient group. A weak positive correlation was present between the blood Tang cell and EPC percentage values in BD (r: 0.318,p= 0.002). It was determined that Tang cell and EPC counts are lower in BD, and these reductions become more profound with increasing disease activity. This situation may prevent the development of a sufficient immune response against a disease with a course of chronic inflammation or may trigger the formation of autoreactive immunity. A reduction in Tang cells and EPCs may serve as a marker or predictor of vascular damage in BD patients and represents the progression of vascular injury.