"The takeover is an important building block in Axel Springer's strategy to increase its digital reach, extend its journalistic portfolio in the English-language space and to grow with innovative digital journalism," the company said in a statement.
Springer, which owns major German newspapers Bild and Die Welt, already had a nine percent stake in BI and is buying 88 percent more of the company's shares to achieve a controlling stake, with the deal putting the total value of the company at €395 million ($442 million).
But around three percent of BI will still be owned by Amazon founder Jeff Bezos' personal investment firm Bezos Expeditions.
"By acquiring BI, we're continuing our digital growth strategy and investing, as we've said, in digital journalistic businesses in the Anglo-American space," Axel Springer CEO Mathias Döpfner said in the statement.
Springer has been hunting for English-language acquisitions ever since losing out on a deal to acquire the Financial Times in June to Japan's Nikkei.
The Germans say they are particularly interested in BI's audience of so-called "millennials" - people aged 18 to 34 - interested in business news.
"If you look at what Springer has been up to recently, they're trying to extend themselves as a platform" for online news, professor of media economics and innovation at Stuttgart Media University Mike Friedrichsen told The Local last week when rumours of the deal surfaced.
"Newspapers like Bild are falling away [in popularity] and Springer need to build themselves a second leg to stand on. Business news is becoming more and more of an important factor in the media industry."
Friedrichsen also pointed out that the acquisition would be as much to get hold of BI's creative business journalists as its resources and audience.
"[Springer] have to buy in competence [to develop new ways of delivering business news] because they don't have it in-house either at Welt or Bild," he said.
And indeed, in Tuesday's statement, Döpfner was careful to emphasize that "we're looking forward to creating the future together with Henry Blodget, [Chief Operating Officer] Julie Hansen and the extraordinary Business Insider Team."