The new funding round was Millennial's largest since it was founded more than four years ago. It has raised more than $65 million from investors. The new money comes from several existing investors in Millennial, including Bessemer Venture Partners, Columbia Capital, Charles River Ventures and New Enterprise Associates.
The company said that it plans to use the new equity investment to fund the company's global growth plan this year. It also plans to build on its acquisition of TapMetrics, a mobile analytics company it acquired last year, and consider additional acquisitions this year.
The new funding comes as Millennial, which is competing toe-to-toe in the mobile display advertising market with Google Inc. and Apple Inc., said it tripled revenues last year, though the privately held company does not disclose specific revenue figures.
The company says its mobile ads reach more than 85 percent of mobile users in the United States. The total mobile ad market was estimated at more than $1 billion last year, and is expected to grow quickly over the next few years.
The mobile ad market attracted Google and Apple, who have both bought competitors of Millennial for hundreds of millions of dollars. Several months ago, Millennial was rumored to be in acquisition talks with Research in Motion, maker of BlackBerry smart phones, but the negotiations reportedly fell through.
Paul Palmieri, Millennial's chief executive and co-founder, sees the mobile advertising industry applying to many different kinds of devices, from smart phones and tablet computers to appliances.
"The mobile model continues to expand beyond the phone, and is becoming the new, device based Internet via apps on everything from refrigerators to tablets to televisions," Palmieri said in a statement to The Baltimore Sun.
Millennial currently has offices in New York, London, and San Francisco, plus sales offices in Detroit, Los Angeles, Chicago, Dallas and Atlanta.