The Investec Cup match is scheduled for Tuesday at Heriot's home ground of Goldenacre in Edinburgh.
The Australian-born Pritchard, who plays his club rugby for the Bedford Blues in England, is Canada's all-time points leader.
The 35-year-old fullback qualifies to play for Canada by virtue of his Saskatchewan-born grandfather. His great-grandfather had come to Canada from the United Kingdom to work on a farm just outside Regina.
"Hell of an honour and a lifelong dream to be invited to play for the #Baabaas #CantWait," tweeted Pritchard, who has represented Canada at three Rugby World Cups.
Since 1890, players from more than 25 different countries have played for the Barbarians. Once invited, a player becomes a life member of the famous club.
Fellow Canadians Jason Marshall and Sean Duke played for the Barbarians against the Leicester Tigers last November.
They are part of a select group. Former Canadian captains Al Charron, Gareth Rees and Mark Wyatt have also worn the distinctive black-and-white hooped jersey of the Barbarians.
Charron played five times from 1994 to 2000 while Rees saw action in three games in 1993 and '94. Other Canadian Barbarians include Glen Ennis (1992), Kevin Tkachuk (2006), David Lougheed (1995), Rod Snow (1996 and 2004) and Wyatt (1991).
In the early 1960s, the Barbarians asked Douglas (Buzz) Moore to play against Canada while on tour in Britain. He declined, leading the Canadians to a 3-3 tie against the all-stars. The Barbarians made him an "honorary Barbarian.''
A new roster of Barbarians, known for their free-flowing, adventurous style of rugby, will play Ireland on May 28 and an England XV on May 31.
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