Hitwise helps clients monitor the performance of their websites and target their online advertising spend more effectively.
The transaction is still subject to regulatory approval.
Don Robert, chief executive officer of Experian, said: “We have been successfully repositioning our marketing solutions business to meet our clients' needs as they continue to switch more of their advertising spend online.
“Hitwise, which is a rapidly growing, successful business, brings new, unique data to Experian and complements the existing data, tools and expertise that we already offer to clients in other areas such as research services and email distribution."
Andrew Walsh, CEO of Hitwise, said: "Over the last 10 years, Hitwise has developed a truly unique digital intelligence service that helps inform the online marketing strategies of 1,200 clients around the world every day.
“We are excited to become part of Experian, having worked with them for over four years. We will now be able to accelerate Hitwise's growth and profitability through access to Experian's wider pool of data, tools and clients, while more quickly expanding our global footprint."