With a managerial career spanning over four decades, Still returns to the Bees for a second spell after leaving Dagenham & Redbridge, and will be looking to guide Barnet back to the EFL at the first attempt.
He replaced Martin Allen, who took over at Chesterfield - also relegated out of the Football League - earlier this week.
Barnet chairman Tony Kleanthous told the club`s official website: “After the debacle of last season, I decided that we needed someone who would bring stability and experience to the football management side of the club.
“The more we researched who would be the best candidate, the more the same name kept coming back.
“John knows the division better than any other manager and has won promotion from this division more times than any other manager.
“His remit is to run the football side from top to bottom and I am pleased to welcome him here and to once again work with him.”