The $60 million, which has been invested by an undisclosed "large, Boston-based public equity and asset management" company, will be used to expand the AppNexus team across the world, as well as develop new services.
AppNexus could also potentially use some of the cash to make opportunistic acquisitions and sign partnerships that will improve its product offering.
Brian O'Kelley, the chief executive and co-founder at AppNexus, said: "When we founded AppNexus, our aspiration wasn't just to build the world's best ad tech company – we wanted to prove that you can build a seminal, global technology company right here in New York.
"As a company purely focused on creating great tech, our aim is to continue to revolutionise the advertising industry, and we're just getting started."
JPMorgan was AppNexus' exclusive financial adviser.
The company provides ad technology to both buyers and sellers of internet ads, including WPP and Microsoft.