Retinoblastoma is a rare intraocular tumor of childhood. Chemoreduction followed by laser or cryotherapy is the treatment of choice. Subtenon carboplatin injection is also an accepted treatment modality for vitreous seeds, along with systemic chemotherapy. Transient periocular edema, optic neuropathy and fibrosis of orbital tissues are the known side effects of subteneon carboplatin injection. We report a case of severe aseptic orbital cellulitis with necrosis and prolapse of the conjunctiva 48 h after the injection, which resolved well on only conservative management.