Background: For grafting the left anterior descending (LAD) coronary artery, the left internal mammary artery (LIMA) has become the gold standard. Pedicled and skeletonized methods are the two most common harvesting procedures. Objective: In this study we compared between both techniques regarding incidence of postoperative mediastinitis in diabetic patients. Patients and methods: 80 diabetic patients with controlled diabetes i.e. HbA1c below 7 underwent on-pump coronary artery bypass grafting (CABG) surgery were included in this study. The patients were divided into two groups, according to the procedure applied to harvest the LIMA: Group 1: 40 patients underwent pedicled LIMA and Group 2: 40 patients underwent skeletonized LIMA. After CABG surgery, the cases had a 3-month follow-up time. Results: In the pedicled LIMA group, the frequency of excessive intraoperative usage of bone wax was significantly increased. A significant increase was found regarding the occurrence of sternal wound infections (SWI) in the pedicled LIMA group (22.5%) versus (12.5%) within the skeletonized one, (P-value = 0.003). The univariate analysis of the factors related to SWI in all of the studied CABG patients were obesity [OR (95% CI): 15.61 (5.78-42.12), P <0.001], pedicled ITA [OR (95% CI): 4.3(1.4-12.9), P 0.004], intraoperative excessive use of bone wax [OR (95% CI): 14.53(6.48-32.56), P <0.001], and intraoperative excessive use of diathermy [OR (95% CI): 17.31(7.55-39.4), P <0.001]. Conclusion: In comparison to pedicled LIMA, skeletonized LIMA in CABG was correlated to reduced occurrence of superficial as well as deep SWI among diabetic patients.