The Suns completed a sign-and-trade deal for the point guard.
The 5ft 9 point guard was a restricted free agent this offseason, and after he signed the Suns' offer sheet the two sides quickly came to a sign-and-trade agreement.
The Kings will receive a £7 million trade exception and the rights to forward Alex Oriakhi when the trade is made official.
Yahoo Sports first reported the deal.
Thomas's days were numbered in Sacramento when the Kings signed fellow free agent point guard Darren Collison to be their starter for next season. With a roster featuring DeMarcus Cousins, Rudy Gay and 2014 first-round pick Nik Stauskas, the team are not looking for scoring from the point guard position.
It is easy to see what Thomas will bring to the Suns. He will be the first guard off the bench, playing behind standout guards Eric Bledsoe and Goran Dragic. Thomas will provide instant offense and energy to the second unit - he averaged 20.3 points and 6.3 assists per game for the Kings last season.
After the deal, Thomas expressed his gratitude to the Kings and his excitement at joining the Suns.
Thank you 2 @SacramentoKings organization for giving me a chance. It's been a great 3yrs and I wouldn't change that for nothing.— Isaiah Thomas (@Isaiah_Thomas2) July 11, 2014
The Suns are looking to make the playoffs this season after narrowly missing out with a 48-34 record in 2013-14. The team agreed a three-year deal with free-agent small forward P.J. Tucker on Thursday.