Mann, one of Germany's most renowned writers, penned part of his 1947 novel "Doctor Faustus" in the house located in the ocean-front Pacific Palisades neighbourhood on the edge of Los Angeles.
The German Nobel literature laureate had lived at the property from 1942 to 1951 with his family after fleeing Adolf Hitler's rule. Mann, a strident critic of the Nazis, was also stripped of his German nationality.
"Thomas Mann's house was like the 'White House for exiles'. This was the home for many Germans who fought together for a better future for our country, who battled for an open society and helped built the foundations of common transatlantic values," said Foreign Minister Frank-Walter Steinmeier in a statement.
Among exiled Germans who spent time at the US villa were poet and playwright Bertolt Brecht, the philosopher Theodor Adorno and filmmaker Fritz Lang.
Germany plan to host young resident artists at the house, which was purchased for $13 million (12.2 million euros) according to Süddeutsche Zeitung daily.
Steinmeier said he hoped the site would help to contribute to transatlantic dialogue at a "stormy time, when we need more than ever cultural anchors with our most important partner outside Europe."
The foreign minister had said the election of Donald Trump would make transatlantic relations "more difficult" with the United States likely to make more decisions on its own.