Background: Systemic inflammation and thick, red, scaly plaques on the skin characterize psoriasis vulgaris, which is  a common and varied chronic inflammatory dermatological disorder. IL-26 has been categorized as both an IL-10 family member and an IL-20 subfamily member. This cytokine was first found in T cells that had been modified by the herpesvirus saimiri. Aim of the work: We want to learn more about the relationship between IL-26 levels and the severity of psoriasis by comparing the serum and tissue IL-26 levels of people with psoriasis to those of a healthy control group. Patients and Methods: This study was a case-control research that took place between March 2021 and September 2021 at the Beni-Suef University Hospital Dermatology outpatient clinic. Twenty men and ten females with psoriasis participated in the research, which was approved by the Research Ethics Committee (REC). Patients' ages varied widely, from 28 to 50, with a mean (standard deviation) of (42.50 ±6.5) years. Thirty people who did not have psoriasis (healthy controls) participated in the research. In terms of age and sex, these controls were excellent analogs for the psoriasis patients. Every individual who took part in the study had their whole medical and personal history compiled. The IL-26 Human ELISA kit was used to analyze the concentration of IL-26 in the blood and their expression in tissues. Results: In contrast to the control group of healthy people, those with a psoriasis diagnosis were shown to have significantly higher levels of serum IL-26 and tissue expression. Clinical psoriasis severity, as measured by the Psoriasis Area and Severity Index (PASI) score, was shown to be positively correlated with both the blood level and tissue expression of IL-26. Serum IL-26 concentration was positively and statistically significantly related to Psoriasis disease severity and duration. Serum and tissue levels were not associated with age, gender, family history, onset, or progression of illness in patients. Conclusion: IL-26 may be related to the severity of psoriasis and plays a crucial part in the disease's development. Our research looks at how Interleukin-26 (IL-26) plays a part in the development of psoriasis by analyzing its expression in both tissue and serum samples.