O'Brien penned a one-year contract with AHL Charlotte on Thursday, Mark Divver of the New England Hockey Journal reports.
O'Brien was the 19th overall pick in 2018 by the Flyers, but he never signed after playing three seasons at Boston University. He signed a minor-league deal last season with AHL Toronto, but he was unable to play due to injury. He will try and make his professional debut this season with the Checkers.