The 20-year-old, who has made four appearances for Bolton’s first-team, will stay at Oakwell until January.
It is the second time he will link up with Reds boss Lee Johnson, who signed him when he was in charge of Oldham.
Wilkinson told the club’s official website: “Lee Johnson gave me the chance to join Oldham and play some League 1 football last season so I snapped it up straight away. I did well in my first spell there and then the gaffer called me back just after Christmas for a second spell.
“When Barnsley came in looking to take me on loan I couldn’t turn it down with this being such a big club, great set of fans, good players and big aspirations this season, and of course the chance to work with Lee again.
“Hopefully I can add some goals, I’m big, like to get in the box, create chances and try to play some good football. I’m looking forward to the game tomorrow. It’s been good meeting the boys today and I’m raring to go for the upcoming season.”
Johnson added: “Conor brings real quality, there’s no doubt about that. He’s a big lad, six foot two, but he doesn’t particularly play six foot two, he’s a real master of the ball. He’s got lovely technique off his left foot, nice feet, a strong shot and he can score different types of goals.”