Google said the new policy will give people more relevant search results and help advertisers find customers.
Google has previously faced criticism over the sharing of users data.
The main change applies to users who have Google accounts.
"If you're signed into Google, we can do things like suggest search queries, or tailor your search results, based on the interests you've expressed in Google+, Gmail and YouTube," the company said, explaining the changes.
The revision comes after Google's previous attempt at social networking, Buzz, was shut down.
The company was criticised for inadvertently revealing users' most e-mailed contacts to other participants through the Buzz platform.
Last year, Google and the Federal Trade Commission reached a settlement to prevent Google from misrepresenting how it uses personal information and from sharing a user's data without approval.