This study investigated the effects of asparagus powder supplementation on blood glucose regulation, insulin, lipid profile, and oxidative stress in overweight and obese individuals. Forty-four adults aged 18–59 years participated in a 12-week randomized controlled trial and were randomly assigned to receive either asparagus powder (40 mg/kg/day) or a placebo (maltodextrin, 40 mg/kg/day). Assessments included an oral glucose tolerance test (OGTT), fasting blood glucose (FBG), insulin, homeostasis model assessment of insulin resistance (HOMA-IR) and β-cell function (HOMA-B), lipid profile, and oxidative stress markers (malondialdehyde [MDA], protein carbonyl, and superoxide dismutase [SOD]). In the asparagus group, OGTT at 30 min and low-density lipoprotein cholesterol (LDL-C) significantly decreased, while SOD activity significantly increased (all p < 0.05). In contrast, the placebo group showed significant increases in OGTT at 30 min, insulin, HOMA-IR, HOMA-B, triglycerides (TG), the TG/high-density lipoprotein cholesterol (HDL-C) ratio, and the total cholesterol (TC)/HDL-C ratio (all p < 0.05). Between-group comparisons indicated that FBG, area under the BG curve at 30–120 min, TG, TG/HDL-C, and MDA levels were significantly lower in the asparagus group than in the placebo group (all p < 0.05), whereas OGTT, LDL-C, SOD activity, insulin, HOMA-IR, HOMA-B, and TC/HDL-C did not differ significantly. Other indices, including TC, HDL-C, and protein carbonyl, showed no significant within- or between-group differences. In conclusion, 12 weeks of asparagus powder supplementation partially improved glycemic control, lipid profile, and oxidative stress in overweight and obese individuals. These findings suggest a potential role of asparagus as a complementary nutritional strategy to reduce the risk of diabetes and cardiovascular disease in this population.