Ex-Ospreys boss Sean Holley is to help coach the Scarlets' while Mark Jones assists Wales in the 2013 Six Nations.
after nine years' involvement.
Since then he has worked as a media pundit and coaching consultant and recently revealed he had turned down
"We are fortunate... to have secured the services of someone of Sean's capability," said Scarlets boss Simon Easterby.
"He will also bring a fresh new perspective to our team environment which will be healthy for our coaching group and our squad of players.
"We look forward to his input; he will challenge and support our players which will add to the energy in our group and I know he will put his all into this role with us.
"With the level of experience and professionalism Sean has, he will hit the ground running with the knowledge he has of our region, players and the game in Wales."
Holley said: "It's a close-knit group at Parc Y Scarlets. As a team, the Scarlets are destined to achieve success with the number of exciting players they have with real talent and passion for the shirt they wear."
He became assistant to current London Welsh boss Lyn Jones at the Ospreys when they were launched in 2003.
During that time Holley helped the Ospreys wing Magners League titles in 2004-05 and 2006-07, 2009-10 while they were Heineken Cup quarter finalists three years in a row in 2007-8, 2008-9 and 2009-10.
Following Jones' May 2008 exit, Holley took charge with ex-Wales captain John Humphreys as his assistant for the 2008-09 season.
Current Scotland interim coach Scott Johnson then joined in 2009 to head a three-man coaching team including Holley and they led the side to the Heineken Cup quarter-finals in 2010, where they lost 29-28 to Biarritz.
That disappointment spurred them on to winning the 2010 Magners League, taking the title in the competition's inaugural play-off final against Leinster in Dublin.
However, the Ospreys have not moved beyond the Heineken Cup quarter-finals in subsequent seasons.