Cardiff's rugby chairman Malcolm Childs said, "The acquisition of Phil for our Premiership side is a major fillip for everyone involved in the club. He will act as a consultant to the coaches and players in our squad, taking regular training sessions and, whenever his contractual commitment with Sky Sports allows, he will be in charge of the team on match days. He brings with him invaluable experience and we are sure to benefit from his input."
Davies, who is set to take charge of his first Cardiff training session tomorrow evening, said, "I am very pleased to accept the invitation and to be involved, hands-on, with the Cardiff team.
"Essentially, I see myself giving support wherever I can, whether it is with the players or the coaches. As well as preparing the team every week it will also be an opportunity to look at the structure in the team and backroom staff and to plan their further development.
"I also want to continue the good practices already in place, especially the two-way relationship between the club team and the regional Blues squad where I have a very high regard for the work being done by David Young."
Davies will also continue as head coach to the Wales Under 20 squad and his role with Cardiff has been finalised with the full support of the Welsh Rugby Union.
Joe Lydon, the national body's head of performance and development, said, "Phil is a great asset for Welsh rugby and I am delighted that his talent, experience and expertise will now be used to benefit the players and coaching staff at Cardiff RFC in this way.
"The Welsh Rugby Union must work closely with its regions, premiership teams and divisional clubs whenever possible to align our structures and strategies here in Wales.
"We will continue to look for innovative ways to draw on the talents and experience of individuals within the game for the benefit of Welsh rugby. I am certain it will help Phil in his role with the Under 20's squad.
"I wish Cardiff RFC well and I would like to publicly thank them for the close and positive cooperation which has led to this initiative."