The 33-year-old has played twice for the GUINNESS PRO12 high-fliers this term, but is set to don the famous black and white hoops for the first time against Australia at Twickenham on November 1.
Head coach John Kirwan has named a 27-man squad, which includes New Zealand stars Colin Slade, Dominic Bird, Steven Luatua and Matt Todd
And Kellock is relishing the chance to run out alongside them.
"I've grown up watching the Barbarians and it'll be very special to pull on the Barbarians shirt," said the 6ft 8in lock.
"It's a great honour to be selected and I'm really looking forward to meeting up with the guys.
"The opportunity to play with such fantastic players form all over the world doesn't come around very often.
"I'd like to thank the club for letting me play this match."
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Guinness PRO12
Suite 208, Alexandra House,
The Sweepstakes
Ballsbridge, Dublin 4, Ireland