Purpose: To investigate the clinical features of all patients with acute-onset diplopia presenting to the ophthalmology department. Methods: The notes of every patient who presented with acute onset (<4-week duration) diplopia to the ophthalmology clinic over a 2-year period were reviewed. Data regarding clinical features, underlying aetiology, past medical history, investigations and outcomes were extracted. Results: One hundred and forty-nine patients presented with 53.7% having an isolated third, fourth or sixth nerve palsy, 10.7% a mechanical cause, 10.1% a dysfunction of higher control, 8.1% decompensation of a pre-existing heterophoria, 6.7% idiopathic, 5.4% causes of monocular diplopia and 5.3% another diagnosis. Neuroradiological investigation identified that <5% of patients had a serious underlying pathology, which required immediate management; 80.5% had a diagnosis and underlying aetiology, which were obvious at presentation based only on clinical information and evaluation. Conclusions: Acute onset diplopia is an uncommon and challenging presentation for the ophthalmologist to manage. These results demonstrate that the aetiology is commonly identifiable at the first presentation based on clinical evaluation, only a small percentage require urgent radiological investigation and a small minority of cases are likely to have serious emergent pathology.