His parents were Anne (née Caulfield) and Arthur Herbert Orpen, a solicitor of Oriel, Blackrock, County Dublin.
While attending St Columba's, Orpen published an Irish comic alphabet for the present times in 1881, which was a mix of cartoons and verse mocking Charles Stewart Parnell and the home rule movement.
He collaborated with Percy French on a number of projects, including illustrating Racquetry rhymes (1888) and The first lord liftinant and other tales (1890).
Orpen's architectural illustrations were included in H. Goldsmith Whitton's Handbook of the Irish parliament houses... (1891).
The same year he designed the cover of a satirical pamphlet, The Abbey row, not edited by W. B. Yeats, which mocked The Arrow and the riots at the first production of The playboy of the western world.
Orpen unveiled a bust of Hugh Lane at the opening of the Municipal Gallery of Modern Art on Harcourt Street in 1908.
[1] From 1910 to 1914, Orpen was in an architectural partnership with Page Dickinson, with the two collaborating on plans for the new Dublin municipal gallery and conversion of the Turkish Baths, Lincoln Place.
In 1914, Orpen was appointed a guardian of the National Gallery of Ireland, and lectured at the Dublin Metropolitan School of Art on architectural history in 1914 and 1915.
St Columba's College holds a portrait of Orpen by his brother, William, as well as a memorial stained glass window to him by Catherine O'Brien.