Scottish-based Beattie, which will run the consumer campaign from its Falkirk office, won the business after a five-way pitch.
The campaign, the first of its kind to target Scotland, aims to highlight the regeneration of Cardiff and the ease of access from Scotland to the south-east of Wales for long weekend packages.
The trigger for the campaign is the recent introduction of daily flights from Edinburgh and Glasgow to Cardiff.
Beattie is initially aiming at newspapers in Scotland. Derek Douglas, who will head the account, said: 'We have to explain to travel writers that Cardiff is now accessible.'
Radio and TV programmes, such as Grampian TV's holiday show Scottish Passport, will also be targeted.
WTB chairman Philip Evans, said: 'The aim of recruiting a PR agency in Scotland is to create awareness of Cardiff and Wales as a tourism destination.
Scotland has never been a primary market for Wales.'
Beattie will also promote Wales as a golfing holiday destination. The Celtic Manor Resort, close to the city, is to host the 2010 Ryder Cup. Douglas said it also hopes to tap into some Scots' familiarity with Cardiff as a destination for Six Nations rugby matches.
Research by Beattie suggested that 68 per cent of Scots would consider Wales for a short break but were unsure what the country had to offer or how to get there.