Standing 6 ft 6" tall and weighing 17st 5lb, Earle represented Western Province at age-group and Currie Cup level before moving to the Johannesburg-based Lions in 2010. He switched to the Griquas earlier this year and has since established himself as a regular in the Cheetahs matchday squad.
Earle is expected to arrive in Llanelli in July in time to take part in pre-season with a Scarlets side looking to build on a quarter-final showing in the Amlin Challenge Cup and a fifth-placed finish in the RaboDirect PRO12.
"This is a significant signing for the Scarlets," said head of rugby Nigel Davies.
"George is in his prime as a player and is ambitious to make a mark over here. He will bring a tough edge and different set of experiences from his career in Super 15.
"He gives a new dimension to our second row options and we know we need to enhance and strengthen our set piece play going into the big competitions next season, particularly in Europe.
"It's key to have secured a quality second row who has enough experience but also plenty to give and the hunger to achieve over the next three seasons at Parc y Scarlets. He's an aggressive and focused player with a high work rate and has the ability to add a real edge to our game."
The Scarlets have lost second row duo Dominic Day and Damian Welch to Bath and Exeter respectively in recent weeks and, with that particular pair having played a combined total of 165 games for the region, Davies admits finding the right blend of experience and enthusiasm has been a focal point of the Scarlets' ongoing recruitment drive this summer.
"We've said previously that we wanted to take time to analyse our options carefully as a coaching group and take the time to find the right solutions for this squad," added Davies.
"We need to ensure that any players that are brought into our environment from outside our region are the right fit for our progression and ambitions but also that capable of working with and complementing the group of players we have here.
"This move illustrates the level of player we are committed to recruit, to both strengthen the competitiveness of the squad and ensure we have the right level of senior players in key positions to help mentor and develop a strong group of talented youngsters, as we have done previously with the addition of overseas players like David Lyons and Regan King."