Former Oldham Athletic boss Johnson, 33, currently the third youngest Football League manager, was unveiled at Oakwell on Wednesday afternoon after signing a contract until 2018. He becomes Barnsley's sixth permanent manager in less than six years.
A club statement on Barnsley's official website read: "From the outset the board determined that it was seeking young candidates with strong coaching credentials and astute tactical awareness. A clear and attractive football philosophy and a viable plan to implement that philosophy was also sought.
"The board also gave some credit for a knowledge of our club's current playing contingent, the teams in our division and proven ability to recruit players with development potential.
"A small number of candidates were interviewed and Lee Johnson was selected as significantly the best of these. He met the selection criteria established and also produced a specific plan for Barnsley Football Club for his first 100 days in charge. This included a playing strategy, specific tactics, identified current weaknesses and credible recruitment targets to strengthen our team."