Glasgow wing DTH van der Merwe will join Scarlets in the 2015-16 season.
The 28-year-old Canada international has scored 39 tries in 90 appearances during six years with the Warriors.
"He's a very aggressive defender, has a natural ability to create and score tries and having a strong finisher in your side is invaluable," said Scarlets head coach Wayne Pivac.
"I have heard great things about the Scarlets, I'm looking forward to making the move," said van der Merwe.
"I am extremely grateful to Glasgow Warriors for all that they have done for me since I joined back in 2009.
"I have had six great seasons at Glasgow but I feel that the time is right for me to face a new challenge.
"The Scarlets are traditionally known for their exhilarating style of running rugby and have some great backs in the likes of Regan King and Scott Williams
The South African-born player says he is looking forward to working with former Wales and British and Irish Lions fly-half Stephen Jones who takes up a post as Scarlets' backs coach in the summer.
Pivac has spoken of his concern at a relative lack of experience in the backs at Parc y Scarlets, and believes van der Merwe will be a valuable addition.
"At 28 years of age DTH will add international experience and maturity to our relative young backline and it will be great to have another experienced voice around to nurture some of our younger guys coming through," he added.
"With experience at centre and on the wing DTH will be an exciting new addition to the squad."