The arrangement has the full approval of all four Regions and has been brokered through close liaision with Regional Rugby Wales.
In the year ahead Robin McBryde will now join the Scarlets full time outside the Welsh international RBS 6 Nations calendar, the Invesco Perpetual Autumn Series and the summer preparations for Rugby World Cup 2011.
The deal has been reached to ensure that Welsh rugby achieves the full benefit of Robin McBryde's experience and skill.
He remains a full time employee of the Welsh Rugby Union but will now be seconded to the Scarlets and funded by the Region at all times when operating within their system.
All the Welsh International squad coaches and backroom staff continue to work closely with the four Regions of Wales but Robin McBryde has expert knowledge of the Scarlets through a long term association as player and coach.
McBryde said: "I am very grateful for this opportunity and to have more of a 'hands on' role when I'm not involved with Wales, which should benefit my own personal development as a coach, and in turn benefit the players that I coach.
"Being involved with Wales and the Scarlets as player and then coach throughout my career have been both an honour and a privilege which have shaped my rugby development.
"I remain totally committed to my international role and within that function I have never lost touch with the regions, and having a history at the Scarlets, I am aware of their structures and know some personnel very well.
"International rugby teams need close alignment with the teams which supply their players and I am now perfectly positioned to enhance and develop that through my activity with The Scarlets."
Robin McBryde won 37 caps for Wales, captained the Scarlets for whom he made 250 appearances before joining the Wales management team in the summer of 2006. He was Wales acting Head Coach for the international tour to North America and Canada in 2009.
Wales Head Coach Warren Gatland said: "Robin plays an important role in the Wales squad and this new venture will undoubtedly benefit both the Welsh team and the Scarlets.
"Robin's close links with the Scarlets have made this arrangement possible and I know he has the skill and commitment to make it work well for us all.
"Robin will also personally benefit from the opportunity to work with a team on a day to day basis and to experience the development and progression of this side."
WRU Group Chief Executive, Roger Lewis, said: "I am extremely pleased that we have been able to work together to create this exciting opportunity for a coach of Robin's calibre.
"He is totally committed to achieving excellence and has a great understanding of the demands of modern elite and professional rugby.
"Robin has a special alignment with the Scarlets through his distinguished playing career so it just made sense for us all to work together in the best interests of Welsh rugby.
"I am very grateful to all four Welsh Regions and Stuart Gallacher of Regional Rugby Wales for helping make this pioneering arrangement work."
Scarlets Head Coach Nigel Davies said: "We are very pleased to have secured Robin into our coaching team next season. He brings a wealth of experience from coaching at international level, which will be good for all our players to be exposed to and he'll bring fresh ideas and additional energy to our set-up.
"The fact that he understands our region well, our brand of rugby and what it stands for, is another big plus for us and he has worked with a number of our players already and having that familiarity means he can hit the ground running.
"I know he's keen to learn more from coaching at regional level and will benefit professionally from his time with us as he broadens his coaching skills and experience."