Serum levels of interleukin (IL)-33, IL-36 and IL-37 have been reported to be up-regulated in various T helper (Th)1/Th17 mediated autoimmune/inflammatory diseases. Although IL-33 and IL-36 expression are increased in skin lesions of patients with psoriasis, their serum levels in such patients have not yet been adequately studied. We aimed to evaluate serum level of IL-33, IL-36 and IL-37 cytokines and IL-37 gene expression in patients with autoimmune/inflammatory disease of psoriasis and to explore their correlation with disease severity. Such evaluation further clarifies disease pathogenesis and may be utilized in clinical practice. 47 patients with psoriasis vulgaris and 47 healthy individuals were included. Serum IL-33, IL-36 and IL-37 levels were measured by Elisa and gene expression of IL-37 measured by real time PCR in all participants. The disease activity was assessed by the psoriasis area and severity index (PASI). Linear Correlation between interleukin measures and PASI score was calculated. Also sensitivity and specificity of such measurements were determined. Serum IL-36 and 37 levels in patients with psoriasis vulgaris were significantly higher than those in healthy controls and positively correlated with disease activity (PASI score). Serum IL-33 levels in patients were equal to those in healthy controls but positively correlated with disease activity. Serum IL-36 levels were significantly higher than serum IL-33 levels. Gene expression of IL-37 levels in patients were higher than healthy controls but was not correlated with disease activity. Serum IL-36 and IL-37 levels are generally increased in psoriasis vulgaris and correlated with disease severity. Therefore, serum IL-36 and IL-37 levels may be markers of treatment and diagnosis of psoriasis.