The legendary New Zealand wing, who scored 67 tries in 96 games for the All Blacks, takes charge of a star-studded squad against England, Ireland and Wales.
"As a boy I got up in the early hours of the morning to watch the All Blacks against the Barbarians when Gareth Edwards scored that awesome try in 1973. It inspired me to want to be the best and it was my dream as a player to be a Barbarian. So the honour of being invited to coach them will be one I will remember forever.
"The Barbarians are putting together a very strong squad and our goal on this great tour against England, Ireland and Wales will be to inspire young people to play with flair, ability and passion."
The 2012 summer tour kicks-off with the annual fixture against England at Twickenham on Sunday 27 May and continues with a match against Ireland at Kingsholm, Gloucester two days later. It concludes with a return to the Millennium Stadium for the match against Wales on Saturday 2 June.
Barbarians' secretary Alan Evans added:
"The Barbarians defeated England, Ireland and Wales in their most recent encounters against them and we are very conscious that each of them will be keen to gain revenge this summer. With that in mind, we are in the early stages of assembling a very strong squad to meet the challenges ahead.
"Shane Williams will be making what will be his final representative appearance for us against Wales and also in the squad will be another Welsh record-breaker, Stephen Jones.
"The match at Twickenham will be an opportunity to field Lewis Moody and Iain Balshaw against England, and from further afield we have recruited Joe Rokocoko and Cedric Heymans."
Barbarians Summer Tour 2012
Sunday 27 May v England at Twickenham (2.30pm)
Tuesday 29 May v Ireland at Kingsholm Stadium (7.45pm)
Saturday 2 June v Wales at Millennium Stadium (2.30pm)
Tickets for the Barbarians match against Ireland are priced as follows:
Silver: Adult £36, Concession £28 & Junior £10.
Bronze and JS Stand: Adult £26, Concession £21 & Junior £10.
Shed: Adult £21, Concession £17 and Junior £5.
West Terrace: Adult £15, Concession £12 and Junior £5.
Gloucester Rugby season ticket holders will receive a £2.00 discount
Book tickets online at www.gloucesterrugby.co.uk or call the ticket hotline on 0871 871 8781 option 2.