Rheumatoid arthritis (RA) is a systemic autoimmune disease mainly characterized by painful, swollen, and inflamed joints. Individual, genetic, and environmental factors influence the development of the disease, which causes involvement not only in the joints but also in other extra-articular tissues. However, its etiopathogenesis has not been fully elucidated yet. NLRP3, which is a key component of innate immune system, may contribute to recurrent and chronic inflammation, resulting in inflammation-related diseases. Therefore, we aimed to investigate the expression profile of NLRP3 in peripheral blood mononuclear cells isolated from patients with RA using immunocytochemical approaches in this study. Our findings demonstrated that NLRP3 expression was significantly increased in patients with RA in comparison with the healthy controls (p<0.01). The highest expression among the patient groups was observed in the active period cases and this expression considerably increased as compared to the control group (p<0.01). Patients in the remission period possessed the lowest expression among the patient groups. Since female gender is considered as an independent risk factor for the disease, the effect of gender on expressions was also investigated. NLRP3 was expressed at higher levels in female patients than in males; however, this difference was not significant (p>0.05). The expression patterns of the patient and control groups suggest that NLRP3 may be involved in the development and progression of the disease. To the best of our knowledge, our study is the first research investigating NLRP3 expression profile in peripheral blood mononuclear cells obtained from patients with RA using immunocytochemical approaches. The results of our study highlight significant aspects. However, further research using more sensitive methods with a larger number of cases is required to assess the function of NLRP3 in RA and to provide a deeper insight into the mechanism.