The site received the backing from Palo Alto, California-based Oak Investment Partners and it will use the investment to invest in technology and infrastructure and expand its content offering.
The Huffington Post, founded by Arianna Huffington, plans to launch a new investigative journalism initiative as well as roll out local versions of The Huffington Post in select cities.
The rollout of the site, which now bills itself as the internet newspaper, will see it increasingly take on US newspaper and news websites as it did successfully in covering the 2008 US presidential election.
The announcement was made by Arianna Huffington and an Oak Investment representative will now join the five-person board.
In a statement Huffington, said: "This commitment from Oak Investment Partners will allow us to accelerate our growth, with more verticals, more video, more citizen journalism initiatives, more cities for our local editions, and a fund for investigative journalism."
Kenneth Lerer, co-founders of The Huffington Post, added: "We are thrilled to bring on board a partner like Oak to work with Softbank Capital and Greycroft as we move forward. The additional capital from Oak will enable us to go full-steam ahead with operations and select acquisitions."
Results from a recent comScore study showed that visits to political blogs surged around the election and the Huffington Post, which attracted 4.5m visitors in September, was a big winner with traffic up 472% on a year ago.
Fred Harman, general partner at Oak Investment Partners, said, "Much of the news media business needs to be reassembled online around an ad-supported model and the timetable for this has been accelerated, not slowed, by this economic down cycle.
"We believe that The Huffington Post has built a platform and business model to be among the leaders in aggregating this audience online. Our financing will provide the resources necessary to scale the company, both organically as well as through acquisitions of additional talent and new media companies."