The money has come out of the £40.9m generated by a new round of funding for , led by last month.
Frontline has long-standing relationships with companies including Experian and Reunion.com, as well as interactive ad agencies.
The acquisition of Frontline, including its proprietary data management technology, email products and 25 employees, fuels Adconion's rapid global expansion, including the planned opening of a new office in San Diego.
Frontline further enhances Adconion's offering to advertising agencies and marketers worldwide, including audience targeting, video and email.
Matthias Quadflieg, chief operating officer of Adconion, said: "Audience targeting is often an essential element of the campaigns that advertising agencies create for their client brands.
"The Frontline acquisition will help Adconion arm agencies with the technology necessary to compete in today's evolving media landscape. At the same time, we are extremely committed to respecting personal privacy and already adhere to the stringent European privacy standards."