According to a press release Blau "will work across GNM's editorial and commercial teams, helping them to grow global audiences and revenues by developing new digital platforms that deepen reader engagement and provide new opportunities to commercial partners".
Reporting on the appointment itself, the Guardian added that "in his five years at Zeit Online, Blau tripled the monthly unique user base".
Chief executive of Guardian Media Group Andrew Miller said in the release that Blau's "track record for developing robust business models online make him the ideal candidate to help us make the most of the commercial opportunities generated by our huge and highly-engaged audience".
Zeit Online was one of the winners at last year's Online Journalism Awards, where it took away an award for outstanding informational graphic or data visualisation for its "tell-all telephone" visualisation.
In the same year Blau was also named Germany's 'chief editor of the year' by Medium Magazin, the release adds.
GNM editor-in-chief Alan Rusbridger adds in the release that Blau's "guidance and insight will be invaluable to Guardian News & Media as we continue the journey towards a digital-first future."
The Guardian first announced its digital-first strategy in July last year, at which time it said the group would aim to double digital revenues by 2016.