The Barbarians face England in the Old Mutual Wealth Cup at Twickenham on May 28 (3pm) before taking on Ulster at the Kingspan Stadium in Belfast on June 1 (7.30pm).
Uncapped centre Bundee Aki, who has played 58 times for Connacht, has been named in the initial squad.
Cotter has called up Adam Ashley-Cooper (Australia), Will Genia (Australia), Facundo Isa (Argentina) and Census Johnston (Samoa), who bring a wealth of Test experience with them and those four France-based players will be joined by Corey Flynn (New Zealand) and Bundee Aki.
Wing Ashley-Cooper (116 caps) and scrum half Genia (75 caps) were World Cup finalists in London in 2015, back row forward Isa was one of the stand-out stars of last year’s Rugby Championship and prop Johnston has appeared in three World Cups for Samoa.
"The Barbarians is all about bringing together talented players from different countries and you can see from the first group of players selected that we’ve been able to do exactly that,” said Cotter.
“We want to compete hard and to entertain in the best traditions of the club, so I’m looking forward to working towards that goal with all the players we’ll have on board when we meet up next month.”
The Barbarians will face England for the 16th time since 1990 next month, having won seven and lost eight in the overall series. They then take on Ulster for the first time since 1957 but enjoyed a successful visit to Belfast last November where they beat Fiji 40-7.
Tickets for the Old Mutual Wealth Cup – England v Barbarians – are available now from £5 for kids and £25 for adults. Visit www.englandrugby.com/tickets
Tickets for Ulster v Barbarians, priced from £20 for adults and £12 for juniors, are on general sale at ulsterrugby.com/buytickets For group offers and hospitality packages call (028) 9049 3222.
Bundee Ake Club: Connacht Position: Centre Born: 07.04.1990 Age: 27 Height: 6ft. Weight: 14st 7lb Barbarians record: Uncapped.
Adam Ashley-Cooper (Australia) Club: Bordeaux Position: Wing Born: 27.03.1984 in Sydney Age: 33 Height: 6ft 1in. Weight: 15st 6lb International caps: 116. Points: 185 (37T) Barbarians record: 2010 v SA.
Corey Flynn (New Zealand) Club: Glasgow Warriors Position: Hooker Born: 05.01.1981 Age: 36 Height: 6ft 1in. Weight: 17st International caps: 15. Points: 15 (3T) Barbarians record: Uncapped.
Will Genia (Australia) Club: Stade Francais Position: Scrum half Born: 17.01.1988 in Port Moresby Age: 29 Height: 6ft. Weight: 13st 5lb International caps: 75. Points: 50 (10T) Barbarians record: 2009 v NZ, 2010 v SA.
Facundo Isa (Argentina) Club: Lyon Position: Back row Born: 21.09.1993 in Santiago del Estero Age: 23 Height: 6ft 2in. Weight: 16st 9lb International caps: 25. Points: 25 (5T) Barbarians record: Uncapped.
Census Johnston (Samoa) Club: Toulouse Position: Prop Born: 06.05.1981 in Auckland Age: 35 Height: 6ft 3in. Weight: 20st 6lb International caps: 56. Points: 20 (4T) Barbarians record: 2008 v Aus, 2010 v Eng, Ire.