The spy agency cast the move as an effort to better get out its message and engage directly with the public, but its first Twitter message, sent out shortly before 2 p.m. EDT (1800 GMT), did not indicate there would be major revelations.
It said simply: "We can neither confirm nor deny that this is our first tweet."
The lack of content did not dampen interest: in less than 90 minutes, the CIA account had nearly 84,000 followers, and that number was climbing fast.
The Central Intelligence Agency has long had a public website, and maintains official accounts on YouTube and Flickr, the photo-sharing site.
"By expanding to these platforms (Facebook and Twitter), CIA will be able to more directly engage with the public and provide information on CIAs mission, history, and other developments," CIA Director John Brennan said in a statement.
Among the items to be posted are artifacts from the CIA's (non-public) museum, and updates to its "World Factbook," a compendium of world leaders, maps and similar information.
Critics say the Obama administration is more secretive than its predecessors. It has cracked down on once-normal interactions between reporters and intelligence officials.
In recent directives, Director of National Intelligence James Clapper has banned intelligence officials from speaking to reporters without permission, even about unclassified information, and also from citing news articles based on unauthorized disclosures.
The CIA's Facebook page is www.facebook.com/central.intelligence.agency. Its Twitter "handle" is @CIA.