The AdMob acquisition will enable Google to develop new tools for creating, serving and analysing emerging mobile ads.
The acquisition will also mean Google's clients will be able to target mobile users with its various ad formats.
The internet giant aims to give advertisers and publishers more choice in mobile ad technology, an area that Susan Wojcicki, vice-president of product management at Google, said has "enormous potential" and is "still in the early stages of development".
Both companies have approved the transaction, which is subject to customary regulatory approvals.