Objective: To report a case of iatrogenic retinal detachment due to inadvertent globe penetration during posterior sub-Tenon injection Methods: A 65-year-old female was given posterior sub-Tenon injection of triamcinolone acetonide for pseudophakic cystoid macular oedema. The globe was inadvertently perforated with superior macula off retinal detachment. Results: She underwent immediate pars plana vitrectomy but failed to regain significant vision improvement. Conclusion: According to the literature, retinal detachment as a complication of posterior sub-Tenon injection is rare. This complication may be prevented by adhering to the standard practice of injecting slowly avoiding any undue pressure.