Although Neil announced his retirement from international rugby two weeks ago, the Wales team management and squad members felt so strongly that he should get the chance to sign off properly with one last appearance at the Millennium Stadium that they decided to invite him to bow out in front of Welsh fans against the Baa-Baas.
And to give the occasion added significance, the WRU has agreed to link Neil's final appearance with a major charity push by titling the match the 'Goodwill Game'.
"Neil Jenkins epitomises everything that is good about Welsh rugby and the WRU is delighted that he has agreed to join the Welsh Squad for the game against the Barbarians," said WRU Group Chief Executive David Moffett.
"Neil has risen from the ranks of the Llantwit Fardre mini-rugby team to become one of the world game' biggest stars who has rewritten the record books with his incredible goal kicking achievements.
"His contribution to our national game has been enormous and it is typical of the man that he wanted his final game in his beloved Welsh jersey to be more than about him. That's why we have joined forces with one of his adopted charities, the National Kidney Research Fund, for the game on 31 May to try to raise awareness of the need for more kidney donors."
Neil already carries a donor card and is an enthusiastic campaigner for the Helena's Hope appeal, which is backed by the National Kidney Research Fund in Wales. The appeal was launched by Helena Jones, who has four children affected by kidney disease.
Two have already received transplants, but two more are among 400 patients in Wales who are waiting for suitable donors to be found to help to improve their quality of life.
"It will be a great honour for me to play one final time in the Welsh jersey and it will be extra special coming at the Millennium Stadium. But what will make it an even bigger occasion for me is that the game is being linked to the drive to find more kidney donors in Wales," said Neil.
"I've been a donor card carrier for quite some time. It's great to think that I might be able to benefit somebody when I die.
"It will be a very emotional moment for me on 31 May and I just hope Wales can give the fans something to shout about. It would be great to go out on a winning note, but we're going to need a lot of support and I hope to see as many fans at the game as possible."
The Barbarians have beaten Wales XVs on their last two visits to the Millennium Stadium and Steve Hansen's side can expect another tough task before they head down under for their two Test tour of Australia and New Zealand next month.
Last year the Baa-Baas triumphed 40-25 and a Braam von Straaten touchline conversion brought the tourists a 40-38 victory in 2001. Wales' only victory in five games against the invitation side came in 1996, when Neil converted three of his side's five tries in a 31-10 win.
The first game between Wales and the Barbarians was an uncapped match on 17 April, 1915, which the Baa-Baas won 26-10 at Cardiff Arms Park. That game was arranged to help raise funds for military charities and to boost the Welsh Guards recruitment drive.
As a result of the stirring speeches at half-time, 60 men were enlisted and Â£200 was raised for charity. Eighty-eight years on, the WRU is using its latest fixture with the Barbarians to further benefit charities in Wales.
"The 'Goodwill Game' will not only heighten the appeal for kidney donors, but will also allow other registered charities to apply for tickets to give away to patients, workers and volunteers so they can join in the celebration," added Mr Moffett.
"We have earmarked a number of tickets for this purpose and we are also hoping that Neil will be able to recreate his three greatest kicks for the crowd during the half-time interval to help raise funds for Helena's appeal.
"This game will offer the Welsh fans the perfect opportunity to give Neil Jenkins the kind of send-off he deserves at the end of his international career."
The Kidney Research Fund will be inviting fans to sign-up for donor cards at the game and they are hoping for a major boost to their campaign.
"The fund is absolutely delighted to be linking in with this game and we hope the people of Wales will respond to Neil Jenkins' appeal. This is a major opportunity for us to increase awareness of our work and we will be taking full advantage of the generous offer from the WRU to reward some of our volunteers by giving them free tickets to the game," said Janet Pardue-Woods, director of the National Kidney Research Fund in Wales.
The offer of tickets from the WRU is open to all registered charities in Wales. To take advantage of the offer an official of the charity needs to fax or mail a request on headed paper to the Millennium Stadium Ticket Office, 98 St Mary Street, Cardiff , marking their envelopes 'The Goodwill Game' (02920 822474).