While other Irish players are expected to added to Australian coach Bob Dwyer's squad, Leinster full-back Dempsey is set for his debut in the famous black-and-white hooped shirt.
The Baa-Baas will play two matches on the tour - against Scotland in Aberdeen's Pittodrie Stadium on Tuesday, May 24 (kick-off 7.30pm), and England, in the TIBCO Challenge Match, on Saturday, May 28 (kick-off 3.00pm).
Maggs, Ireland's most capped centre with 69 Test appearances, has played for the Barbarians before - lining out against Scotland and Wales in 2001.
The Baa-Baas' French tour contingent will include Thomas Castaignede and Sebastien Chabal, while several top-ranking Wallabies, Springboks and All-Blacks will also be included in the full tour party.
* Tickets for Scotland v the Barbarians are available from www.scottishrugby.org, the Murrayfield Ticket Centre (Tel: 0044 (0)870 040 1925) and the Aberdeen FC Ticket Centre (Tel: 0044 (0)1224 650434). England v The Barbarbians tickets can be booked at www.ticketmaster.co.uk/Ticketmaster (Tel: 0044 (0)870 9020000)