Davies, Jenkins' coaching deputy at Stradey Park, won 29 caps for Wales between 1988 and 1997, which included helping his country land the 1994 Five Nations title.
Further support roles are expected to be announced in the near future, with Jenkins unveiling his squad for a two-Test summer tour of Argentina next Wednesday.
Ex-Llanelli and Wales hooker Robin McBryde could be in line for a job as forwards coach, but current Wales defence coach Clive Griffiths is to leave, although his contract will be honoured. Griffiths will not tour Argentina.
"Having worked with Nigel within the Scarlets regional set-up, I have always been aware of his potential to become an international coach of the future," said Jenkins.
"He has made a huge amount of progress within the top end of professional coaching, and his role as Llanelli Scarlets backs coach has seen him coaching and developing a crop of current Welsh international backs including Dwayne Peel, Mark Jones, Tal Selley, Barry Davies and Matthew Watkins.
"Outside of his technical abilities, Nigel and I share a strong view on a Welsh way of playing rugby and a Welsh ethos. This is an important addition to the team, which will hopefully be strengthened further over the coming weeks."
Griffiths, meanwhile, says he will now "pursue other offers" after being told he would not be involved in Jenkins' coaching team.
"In a way, I understand Gareth's point of view, but I am disappointed at leaving international rugby because it has played a major part of my professional coaching career and life over the past 16 years," said Griffiths, who played a key role during Wales' Six Nations Grand Slam success two seasons ago.
"I will now pursue other offers, and I look forward with huge anticipation to taking up a new challenge within a vibrant, club environment."
Jenkins added: "I recognise the work Clive has done with the Wales squad - he was a big part of the success the team has enjoyed over the past two seasons - but my view going forward is that it is important for me to create a new coaching environment with a new coaching team around me.
"I have had open discussions with Clive, and I have explained this to him.
"He felt that rather than stay on for the tour of Argentina, it was better for him to concentrate on new opportunities elsewhere."