Background: Vitiligo is an autoimmune depigmenting disorder of the skin, characterized by well-defined macules and patches due to melanocyte destruction. Sialic acid (SA) possesses antioxidant properties, decreases the activity of anti-melanocyte antibodies and soluble interleukin-2 receptors (SIL-2R), as a result decreasing immune-mediated melanocyte injury. Thus, strengthening its role for unstable vitiligo and encouraging cessation of disease progression Objectives: This study aimed to evaluate the serum level of sialic acid with the activity of vitiligo. Patients and methods: This case control study included patients with non-segmental vitiligo (NSV). They were divided into 2 groups: Group A included 30 patients with active vitiligo and group B included 30 patients with stable vitiligo. Control group (C) included 30 age-matched participants. Dermoscopic examination was done by BPLeFoSK criteria for stability in vitiligo and examination of active vitiligo clinically was done by VETI score. Sialic acid was detected by enzyme-linked ‎immunosorbent assay (ELISA). Results: There was no significant difference between active and stable groups as regards median VETI. There was a significant increase in serum sialic acid among active followed by stable and the least in control group. There was a significant difference between stable and active disease as regards dermoscopic findings. Insignificant relationship was detected between VETI and sialic acid, and age in groups A and B. Conclusion: In terms of vitiligo cases, serum sialic acid was significantly increased among active, followed by stable, and the least was for control. The studied parameters could act as an essential modality for monitoring vitiligo activity.