Objective: Although the frequency of metabolic syndrome has been studied separately in psoriasis, psoriatic arthritis (PsA), and rheumatoid arthritis (RA) patients, there is no study that compares the prevalence of metabolic syndrome in all three diseases. The purpose of this study is to evaluate the relationship between metabolic syndrome (MetS) and chronic low-grade inflammatory diseases, and to determine the frequency of MetS and insulin resistance in psoriasis and PsA as compared to RA.Methods: A total of 155 patients were included in this cross-sectional study. Fifty patients who were diagnosed with psoriasis, 55 PsA patients who were diagnosed according to the CASPAR criteria, and 50 seropositive RA patients who were diagnosed according to the ACR/EULAR 2010 classifica-tion criteria were included in this study. MetS was diagnosed by the 2005 criteria of International Diabetes Federation. The cardiovascular risk factors and parameters associated with MetS were evaluated.Results: The patients’ mean age was significantly higher in the RA. MetS was determined in 33.5% of all patients and MetS and insulin resistance showed no significant difference among the three groups (psoriasis: 36%, PsA: 29%, RA: 36%; p: 0.684 and psoriasis: 70%, PsA: 64%, RA: 66%, respectively; p: 0.785). Triglyceride levels were higher in psoriasis and PsA as compared to the RA (psoriasis: 34%, PsA: 32.7%, RA: 16%, respectively; p: 0.045). The frequency of hypertension was 38% in the RA, which was higher than PsA and psoriasis (p: 0.011).Conclusion: In all three groups, the prevalence of MetS was shown to be higher than the general population. The lack of difference between these groups may be due to the small number of patients, the retrospective study design, and the inequality of the population with respect to age and gender.