The commission approved the deal without any conditions and said it "would raise no competition concerns."
The cable company submitted a $31 billion offer for Sky in April, prompting the European pay-TV group to drop its support for a lower offer from Rupert Murdoch's Twenty-First Century Fox.
Earlier this week, Comcast announced a $65 billion bid for Fox assets that are currently in an agreement to be acquired by Disney in a move that could set off a bidding war. That includes Fox's movie studios, stakes in Hulu, Sky and Endemol Shine Group, as well as networks FX, Star TV and National Geographic.
Comcast is also going after the 61 percent of Sky not already owned by Fox in an effort to boost its international footprint. The company, like other pay-TV distributors in the U.S., is facing more pressure in the video business as more consumers cut the cord, or drop big cable bundles in favor of cheaper streaming options like Netflix.
Comcast said it expects to complete the Sky deal before the end of the year.
Disclosure: Comcast is the owner of NBCUniversal, parent company of CNBC and CNBC.com, and is a co-owner of Hulu.