A 60-year-old Chinese patient was seen multiple times in the ophthalmology outpatient department due to persistent anterior-chamber inflammation and raised intraocular pressure. The patient was being treated with topical corticosteroids and oral acyclovir. Signs of corneal endotheliitis were observed in subsequent follow-ups. A clinical diagnosis could be made on slit-lamp examination, but aetiology could not be specified. An anterior-chamber diagnostic tap performed 18 months after the initial presentation revealed cytomegalovirus (CMV). Prompt response was noted with oral valganciclovir treatment. Our case highlights the importance of performing anterior-chamber tap in cases with persistent anterior-chamber inflammation. There was a long interval between the presentation and diagnosis mainly due to the absence of any concurrent ocular signs. An anterior-chamber tap was delayed until the ocular signs were suggestive of CMV endotheliitis. Timely diagnosis in such cases can improve the outcome as well as the prognosis.