The 36-year-old moves to Shielfield from Penicuik Athletic, having previously been in charge of Edinburgh United and Haddington Athletic.
Vice chairman John Bell told the club website: “Johnny made a real impact on the interviewing panel with his infectious enthusiasm, attention to detail and a real desire to do well at Berwick Rangers.”
His first game in charge of the Ladbrokes League 2 club will be Saturday's Scottish Cup second-round tie against Gretna 2008.
