Background: Diabetic macular edema (DME) is the predominant ocular consequence of DM and poses a significant risk to patients' vision. Objective: This study aimed to evaluate the effectiveness of posterior subtenon injection of triamcinolone acetonide (PSTA) compared to intravitreal triamcinolone acetonide (IVTA) prior to argon laser photocoagulation on the best corrected visual acuity (BCVA) in DME. Patients and methods: This study included 60 eyes with clinically significant macular edema divided into 3 groups of 20 eyes each. Group I received IVTA treatment followed by laser photocoagulation, whereas group II underwent PSTA treatment followed by laser photocoagulation. Group III received treatment solely by laser photocoagulation. Results: In this study we found that IVTA as an adjunct to laser improved the CMT in 80 % of patients, while PSTA as an adjunct to laser improved the central macular thickness (CMT) in 85 % of patients and laser alone improved only 55% of patients. The percentage of patients who showed an improvement in BCVA at the end of the follow up period was 85 % in the IVTA group and 80 % in the PSTA group and laser alone improved only 55% of patients. IVTA caused a higher rise in IOP and cataract than PSTA, and the IVTA group the risk of complication was higher with IVTA such as disastrous ones such as endopthamitis and retinal detachment. Conclusion: PSTA injection was comparable to IVTA injection as an adjunctive treatment to argon laser photocoagulation in DME, and better than laser photocoagulation alone.