Diabetes mellitus (DM) is a prevalent comorbidity among patients undergoing major abdominal surgery and has been associated with adverse surgical outcomes. This study aims to compare the surgical outcomes in diabetic and non-diabetic patients undergoing major abdominal surgery, with a focus on complication rates, length of hospital stay, and overall mortality. Objective: To assess the impact of diabetes on surgical outcomes in patients undergoing major abdominal procedures. Methods: This case-control study was conducted over a period of 18 months and included 400 patients, divided into two groups: diabetic patients (n=200) and non-diabetic patients (n=200). The primary outcomes measured were post-operative complications (such as infection, bleeding, and delayed wound healing), length of hospital stay, and 30-day mortality. Statistical analysis was performed using SPSS, with p-values less than 0.05 considered significant. Results: Diabetic patients had a significantly higher rate of post-operative complications (32% vs. 18%, p=0.002), a longer hospital stay (9.4±3.1 days vs. 7.1±2.4 days, p<0.001), and a higher 30-day mortality rate (5.3% vs. 1.0%, p=0.004) compared to non-diabetic patients. Conclusion: Diabetes significantly impacts surgical outcomes in patients undergoing major abdominal surgery, with increased complications, longer hospital stays, and higher mortality rates. Preoperative optimization of diabetic control may improve surgical outcomes.