Activision said it was paying $18 (£11.70) per share under the deal - a 20% premium on King's share price - and the company would continue to be run by its existing management team.
It meant that Activision was paying less for King stock than investors did on its New York Stock Exchange flotation in March last year.
Candy Crush Saga is one of the world's most successful mobile games
Its value fell on day one and failed to take off as the company struggledto match the success of Candy Crush with its new offerings.
Bobby Kotick, the chief executive of Activision, said: "The combined revenues and profits solidify our position as the largest, most profitable standalone company in interactive entertainment.
"With a combined global network of more than half a billion monthly active users, our potential to reach audiences around the world on the device of their choosing enables us to deliver great games to even bigger audiences than ever before."
He added: "Activision Blizzard will provide King with experience, support and investment to continue to build on their tremendous legacy and reach new potential.
His counterpart at King, Riccardo Zacconi, said: "We are excited to be entering into this acquisition with Activision Blizzard.
"Since 2003, we have built one of the largest player networks on mobile and Facebook, with 474 million monthly active users in the third quarter 2015, and our talented team has created some of the most successful mobile game franchises.
"We believe that the acquisition will position us very well for the next phase of our company’s evolution and will bring clear benefits to our players and employees."
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