Objective: Toxic anterior segment (TASS) is a rare acute sterile anterior segment inflammation that typically develops within 12 to 24 hours after an anterior segment surgery. The purpose of this case report is to alert surgeons to the possibility of this complication following any anterior segment surgery, including trabeculectomy, and to highlight the possible etiologies and measures to prevent it.Patient and method: A 58-year-old male glaucoma patient was initially managed medically for primary open angle glaucoma with antiglaucoma medications. There was rapidly progressive glaucomatous optic nerve damage in his left eye within the following year, despite the use of antiglaucoma medications, hence the need for trabeculectomy.Result: The post-operative condition of the patient’s eye was stormy with diffuse limbus-to-limbus corneal edema and profound Descemet’s membrane folds, among other features of TASS, with associated deteriorating visual acuity. Conclusion: Although there is no documented report of TASS following trabeculectomy with mitomycin C, surgeons should be alerted to this possibility. Preventive measures include extreme care to avoid errors while preparing and administering diluted solutions, especially medications that are administered into the intracameral space.