The 26-year old German-born USA international has signed a four-year deal with die Fohlen which will run from this July until the summer of 2018.
Johnson, who can operate at left-back or on the left side of midfield, will see out the remainder of the Bundesliga season with Hoffenheim before departing the Rhein-Neckar-Arena after initially arriving from Wolfsburg in 2011.
"Fabian Johnson is a very interesting player, moreover he is a free agent, who can play at left-back and at left-midfield," Monchengladbach sporting director Max Eberl told Borussia.de.
"We are delighted that he has opted to play for us."
Since being with Hoffenheim, the Munich-born defender has played 75 times in Germany's top flight, scoring five goals and providing 13 assists.
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