The deal is worth approximately £3.8bn ($5.9bn).
Activision has commented on the deal, saying that it puts them at the forefront of interactive entertainment globally, spanning console, PC and mobile platforms.
It also said that after the takeover, the company will have over half a billion active users covering 196 countries.
Candy Crush Saga has been one of the most popular mobile games in recent years, while Call of Duty has been one of the best selling console games.
Computer game publishers are now switching to digitally releasing games as a reaction to the massive growth in the market.
The chief executive of Activision Blizzard, Bobby Kotick, said: “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 also told Reuters that the firm wanted to reach a new audience and appeal to a larger demographic.
Mr Kotick also said that out of King’s players, around 60% were female, and that no hardware or games console was needed to access its games, apart from a smartphone.
King Digital Entertainment’s business model has enabled all users to play its games for free, with the option to buy extra content or power-ups through microtransactions.