Oxidative stress is a central driver of atherosclerosis progression, promoting lipid peroxidation, vascular inflammation, and hepatic metabolic dysfunction. Forchlorfenuron (KT-30), a cytokinin-like plant growth regulator widely used on fruits such as kiwifruit, grapes, and watermelon, has been reported to elevate serum cholesterol levels, suggesting potential atherogenic effects. However, whether KT-30 induces oxidative stress and accelerates atherosclerosis remains unknown. Here, apolipoprotein E-deficient (apoE^−/−) mice were orally administered KT-30 (5 mg/kg/day) for four weeks. KT-30 significantly accelerated atherosclerotic lesion formation, elevated plasma cholesterol levels, upregulated scavenger receptors SR-A and CD36, and downregulated ABCA1 and LXRα, indicating impaired reverse cholesterol transport and enhanced foam cell formation. KT-30 also increased pro-inflammatory cytokines (IL-1β, IL-6, MIP-2) and aortic expression of F4/80 and VCAM-1. Critically, KT-30 exposure was associated with elevated oxidative stress markers, as evidenced by elevated plasma MDA levels, increased aortic 4-HNE immunostaining, and upregulation of NOX-1/4. In the liver, KT-30 induced lipid accumulation, characterized by elevated cholesterol and free fatty acids, accompanied by SREBP-1/2-driven de novo lipogenesis and impaired lipoprotein uptake. Proteomic analysis revealed significant alterations in mitochondrial oxidative phosphorylation- and sirtuin signaling-related protein expression. Taken together, KT-30-associated oxidative stress, accompanied by upregulation of NOX-1/4 and alterations in mitochondrial pathway-related protein expression, may represent an important mechanistic link between lipid homeostasis disruption and accelerated atherosclerosis in apoE^−/− mice, highlighting the potential pro-atherogenic effects of KT-30 in a susceptible experimental model and providing mechanistic evidence that warrants further investigation of its possible cardiovascular implications.