Background: Galectin-3 is a one of the galectin family and produced by T-lymphocytes and has an important role in the inflammation process. Aim: the aim of this study was to determine the levels of serum galectin-3 in patients with psoriasis Vulgaris, a T-cell-mediated inflammatory disease, and investigate the correlation between these levels and activity of disease. Material and Method: this study included thirty-six patients with psoriasis Vulgaris and 30 healthy subjects. The psoriasis area and severity index (PASI) were calculated and recorded for every patient. The patients were divided into three groups; group I (mild), II (moderate) and III (Severe) according to the PASI scores. ELISA analysis was used to analyze the level of serum galectin-3. Results: level of serum galectin-3 in psoriasis Vulgaris patients was significantly lower than the control group (p=0.001). there was a negative correlation between level of serum galectin-3 and PASI scores (Spearman's rho=-0.749, P