OBJECTIVE: Atherosclerosis (AS) is a chronic inflammatory vascular disease characterized by dysregulated lipid homeostasis and plaque formation. Consequently, there is an ongoing need for therapies with high efficacy and low toxicity. Thus, this study aimed to investigate the effects of guggulsterone (GS) on atherosclerotic plaques in mice and to elucidate the molecular mechanisms underlying the beneficial effects of GS in this pathological context. METHODS: A total of 53 male ApoE-/- knockout mice were fed on a high-fat Western-type diet for 8 consecutive weeks to induce atherosclerotic lesions; three mice were randomly selected for model validation by serum lipid analysis and histopathological examination, and were excluded from subsequent grouping. The remaining 50 mice were randomly assigned to five groups (n = 10 per group): model group, low/medium/high-dose GS treatment groups (35/70/140 mg/kg GS, respectively), and an atorvastatin (AT) group (2.6 mg/kg). An additional 10 C57BL/6J mice served as the normal control group. After 8 weeks of intragastric treatment, serum lipid levels (Total cholesterol [TC], Triglycerides [TG], Low-density lipoprotein-cholesterol [LDL], High-density lipoprotein-cholesterol [HDL]) and a composite AS index were analyzed using standard biochemical methods. Serum nitric oxide (NO), monocyte chemoattractant protein-1 (MCP-1), interleukin-6 (IL-6), and prostacyclin (PGI2) levels were measured by enzyme-linked immunosorbent assay (ELISA). Aortic pathological changes were evaluated by hematoxylin and eosin staining, while monocyte/macrophage-specific monoclonal antibody 2 (MOMA-2) and α-smooth muscle actin (α-SMA) expression were evaluated by immunohistochemistry; Aortic Hmgcr and Srebp2 mRNA levels were quantified using reverse transcription quantitative polymerase chain reaction (RT-qPCR). Outcome assessments were conducted in a blinded manner. RESULTS: Compared with the control group, the model group exhibited poorer general status, increased body weight, abnormal lipid levels, elevated levels of inflammatory factors, and typical aortic AS pathological changes (all p < 0.05), together with the upregulation of aortic Srebp2 and Hmgcr mRNA levels (all p < 0.05). In contrast, mice in the medium- and high-dose GS groups and the AT treatment group exhibited improved general status, reduced body weight, normalized lipid levels and inflammatory factors, and ameliorated aortic pathological damage, along with the reversal of the molecular changes observed in AS model mice (all p < 0.05). Notably, high-dose GS exerted comparable or even superior regulatory effects versus AT on the levels of TC, TG, LDL, NO, PGI2, IL-6 and MOMA-2. CONCLUSION: GS treatment reduces atherosclerotic plaque area and delays AS progression in mice, potentially through the regulation of Srebp2/Hmgcr mRNA expression, thereby improving lipid metabolism, inhibiting inflammatory responses, and enhancing autophagy.