The deal was first reported in May, but according to tech website VentureBeat the deal was finalized Thursday, with both companies declining to comment on the development.
"We don't comment on rumor or speculation," a Google spokesperson told PCMag.
The acquisition, the biggest by YouTube, suggests Google is hoping to add video gaming to its online video service. Twitch, which was founded in 2011, lets users post videos of their gameplay or live stream their games to online viewers. Currently, the service has 50 million unique users, with seven million people on the site every day and 1.1 million users posting videos every month.
Twitch released an app on Microsoft's Xbox One at the same time Titanfall was released. Shortly thereafter, Microsoft announced players had live streamed 10 million minutes of battles, making the game the most-streamed on the console.
According to a recent report from Sandvine, Twitch.tv generates more more traffic online than HBO's online service, HBO GO. Twitch has become the most popular service for watching and streaming video gameplay.
Google has recognized the growth seen in the online streaming industry and last month announced a new feature on Youtube that notifies users if the creator of the video they are viewing is streaming live gameplay at that time.