Measuring 50cm x 76cm (19.6in x 30in), it was bought by a Welshman living in England at Rogers Jones & Co auctioneers in Colwyn Bay on Saturday.
Its guide price had been £200-£300.
The poster features soldiers beside a cannon, with the caption: "Anibyniaeth sydd yn galw am ei dewraf dyn" - or "Independence calls for its bravest man" in English.
A World War One recruitment poster written in Welsh has sold at a Conwy county auction for £440.