Background: Rheumatoid arthritis (RA), is a disease that happened because autoimmune and inflammatory effects, it is mean that the human immune system offence healthy cells in the body mistakenly, resulting in inflammation (swelling) in the impacted portions of the body. Osteoarthritis (OA) is treated as the most famous form of joint arthritis. Objective: It is a slowly developed, disabling joint problem that decrease quality of life (QOL) and affects 14% of adults ages 25 and older and nearly 34% of those ages 65 and older. Interleukin elevation levels have been linked to autoimmune and degenerative diseases, thus in the current study. Methods: We tried to evaluate the level of interleukins (IL-35 and IL-38) in the two diseases and found the relationship between immune system response and disease severity. Three groups (RA, OA and control) have been used in the study. Results: The comparison between the three groups has been done and the results show a high significant increase in the level of IL-35 and IL-38 in both patients groups (RA and OA) as compared with control (p<0.001). Furthermore, a highly significant (p<0.001) elevated Na level with a significant (p<0.001) decrease in K and Ca levels was found in the RA and OA patients compared with the control. Conclusions: The study shows that the rise in the levels of IL-35 and IL-38 declares the instinctive role of interleukins and the immune system in the regulation and severity of RA and OA diseases, the role of this parameter may be clear in the controlling and monitoring the progression of diseases.