Sky Sports revealed on Thursday that a compensation fee had been agreed with St Mirren to allow the 20-year-old to join their Championship rivals subject to a medical.
McGinn passed his fitness test despite missing the end of last season due to an injury picked up in a bizarre training- ground incident. He was accidentally spiked in the thigh with a pole by St Mirren captain Steven Thompson and needed hospital treatment.
He subsequently missed the final five matches of the season as the Paisley club were relegated and has since opened legal proceedings, which are ongoing.
Speaking to Hibernian’s official website, McGinn said: “There were other options available but once I weighed it all up I quickly realised Hibs was the right move for me at this stage in my career.
“The manager is really ambitious and I wanted to be part of his plans to move Hibs forward and get the club back into the Premiership. I’m still a young player and I believe Alan Stubbs will help me develop into becoming a better player.”
McGinn becomes Stubbs’ seventh signing of the summer, joining Mark Oxley, Antonio Reguero, Marvin Bartley, Dan Carmichael, Martin Boyle and James Keatings at Easter Road.
And former Celtic and Everton defender Stubbs believes his club have brought in a player with real prospects for the future.
“We are delighted that John has signed,” he said. “His arrival symbolises our ambitions for the future. He is an extremely talented young player with huge potential and I’m looking forward to seeing John continue his development here.”