Ticket prices for the game have been set to encourage families and groups to head for Cardiff to enjoy a special rugby occasion in the capital.
The match has been arranged to commemorate the 130th anniversary of the formation of the Welsh Rugby Union.
To mark the occasion a massive choir of up to 1,000 voices has been invited to attend so that the singing before and during the game will raise the roof.
A host of big name stars will form the Barbarians line-up as Wales coach Warren Gatland names his side with one eye on preparations for the forthcoming Rugby World Cup in New Zealand.
With the game kicking off at 2.30pm families will be able to enjoy the attractions of the city before taking in the party atmosphere inside the Millenium Stadium before the big game kicks-off.
The fixture is the first of four summer clashes to test Warren Gatland's Wales squad ahead of the 2011 Rugby World Cup, with a double header against England and a visit from the Pumas set for August.
Warren Gatland will name his Rugby World Cup squad in August before Wales head south to kick-off their campaign against South Africa on September 11.
Millennium Stadium Manager, Gerry Toms, said: "There is a feast of superb summer rugby just around the corner for all rugby fans with their eyes on their national side ahead of the 2011 Rugby World Cup.
"I'm delighted that the home of Welsh Sport will be hosting the majority of the action, kicking-off with Wales versus the Barbarians on June 4..
"A host of huge rugby names have already been announced to join the Baa Baas in Cardiff for the first of four World Cup warm-up games for Wales and the excitement is building for a spectacular afternoon of rugby for all the family.
"The 2.30pm kick-off is bound to be attractive to families with children who may want to enjoy the city in the morning before watching a great game of rugby and then heading home in good time."
The complete summer 2011 line-up is:
4 June Wales v Barbarians (Millennium Stadium)
6 August England v Wales (Twickenham Stadium)
13 August Wales v England ( Millennium Stadium)
20 August Wales v Argentina (Millennium Stadium)
Tickets remaining for the summer RWC warm-up fixtures against the Barbarians and England at the Millennium Stadium are priced at £40 and £30 for adults, £100 for a family ticket (2 adults 2 children) for the Baa Baas game and £110 family ticket for the England match, with a new category introduced this season of £15 for the under 18s enclosure.
The final game on home soil is against Argentina and is priced at £30 and £20 for adults, £70 for a family of four and £15 for the under 18s enclosure.
Tickets can be purchased online at www.wru.co.uk/tickets or by calling the ticket hotline 08442 777 888 or Ticketline on 02920 230130.