The agreement takes effect immediately, with Microsoft delivering contextual ads, which are based on what the user is viewing, for CNBC.com later this month. Display ads will start in March.
CNBC.com draws 2.6 million visitors a month, many of whom, according to Microsoft, represent a high-quality audience that advertisers are eager to reach.
Microsoft has struck similar advertising syndication deals with Digg.com, a site that lets readers recommend articles to others, and social networking site Facebook.
Securing advertising syndication deals allows Microsoft to offer advertisers a wider pool of Internet sites for ad delivery. It is part of Microsoft's push to gain ground on Google Inc and Yahoo Inc in the $40 billion market for Web advertising.
CNBC is a unit of media and industrial conglomerate General Electric Co.