Craigie Taylor International and its Scotland-based associate RiversGani Communications have been appointed to handle international media relations for the bid.
The agencies have been hired by the Euro 2008 bid committee, backed by the Scottish Football Association and the Football Association of Ireland, and will work up until the UEFA decision in December this year.
The agencies report to the marketing director for the Euro 2008 bid, Simon Lyons, and will work alongside existing retainee Beattie Media, which continues to manage communications with the business press.
The bid was launched last month following a last-minute deal between the two nations, when the Scottish Executive refused to back a solo Scottish bid. Though Ireland will provide just two of the eight stadia required for the tournament, political wrangling continues over whether the Irish stadia should be an upgraded Landsdowne Road, Gaelic football's Croke Park or, more controversially, a purpose-built new stadium.
There are also joint bids from: Austria and Switzerland; Croatia and Bosnia-Herzegovina; and Greece and Turkey. Hungary and Russia have lodged solo bids, while Denmark, Finland, Norway and Sweden are keen on a four-way share.
Formal bidding documents will be submitted in May.
Glasgow's Hampden Park would host the final.