O’Connor, who has left Leicester City, has signed a one-year deal at Fir Park and plays in the same position as Scotland international Declan Gallagher who left ’Well this summer to join Premiership rivals Aberdeen.
“Darragh is a young centre-half who has been with us for the last couple of weeks,” ’Well boss Graham Alexander told the club website.
“We really like what we’ve seen with his attitude and commitment to the game.
“He’s a young player with a lot of potential, but we also think he’s got the capability to break into our first team and compete with our more senior players.
“We’re delighted to have him on board.”
O’Connor made six appearances for Leicester in the EFL Trophy over two seasons, as well as featuring 15 times in Premier League 2.