Background: Regulatory T (Treg) cells are a class of anti-inflammatory lymphocyte subpopulations with a potential protective effect against atherosclerosis, whereas T helper 17 (Th17) cells have been reported to possess proatherogenic activity. It was believed that disturbed circulating Treg/Th17 balance was associated with the onset and progression of atherosclerosis. This study is designed to probe the regulative action of serum Nod-like receptor protein 3 (NLRP3) on the Treg/Th17 balance in patients with atherosclerosis. Methods: Fifty-two patients with coronary atherosclerosis and stenosis degrees of more than 50% were assigned to the coronary artery disease (CAD) group, and an equal number of people without coronary atherosclerosis were assigned to the control group (assessed by coronary angiography). Peripheral blood mononuclear cells (PBMCs) from two group patients were extracted and cultivated. The calculation of the Treg/Th17 ratio and quantitative analysis of the Treg and Th17 cell frequencies were performed through flow cytometry. Real-time fluorescence quantitative polymerase chain reaction (RT-PCR) was executed for the quantitative mRNA detection of the fork head-winged helix transcription factor (Foxp3) and the retinoic acid-related orphan nuclear receptor C (RORC) in PBMCs. Enzyme-linked immunosorbent assays were applied to measure the serum level of NLRP3, interleukin (IL)-10, IL-1\beta, IL-17A, IL-23, and transforming growth factor (TGF)-\beta1. Additionally, the connection between serum Treg/Th17 ratio and NLRP3 levels was analyzed using the Pearson correlation coefficient. Results: The baseline parameters, including sex, age, or blood biochemical indices had no difference in both groups (p > 0.05). The CAD group showed higher Th17 cell frequency, lower Treg cell frequency, and a lower Treg/Th17 ratio when compared to the control (p 0.05). Consistent with the variation in the T-cell subset ratio, in patients with atherosclerosis, the Th17-cell-related transcription factor RORC showed a markedly higher mRNA level (p 0.05), conversely, the mRNA expression of the Treg cell-related transcription factor Foxp3 was notably reduced (p 0.05). Similarly, the serum levels of NLRP3, IL-17A, IL-1, and IL-23 were significantly enhanced in CAD group but IL-10 and TGF-\beta1 were reduced (p 0.05). Additionally, a negative correlation was found between NLRP3 and the Treg/Th17 ratio (r = –0.69, p 0.001). Conclusions: Due to the potential impact on the serum Treg/Th17 ratio, NLRP3 may act as an aggravator in the onset and progression of atherosclerotic disease.