Premier League Huddersfield Town netted a late goal to win 1-0 at Oakwell.
The Reds' most high profile of pre-season friendlies turned out to be a game of few chances but Huddersfield took their final one with new signing Steve Mounie poking in on 89 minutes.
New signing Joe Williams started in midfield and Ike Ugbo was named alongside Stefan Payne up front.
Barnsley created the better chances of a quiet first half with Payne unfortunate not to give Barnsley the lead on 22 minutes when his header from Alex Mowatt's cross was kept out by Jonas Lossl.
Mowatt then fired wide after working a free kick well with former Terrier Adam Hammill.
Phil Billing curled a shot just wide of Adam Davies' goal at the other end.
Joe Lolley's long-range strike was the last chance of the half but his effort flew just over the bar.
Adam Davies came to Barnsley's rescue in the second half when he tipped what looked like a certain goal from Collin Quaner away from goal.
Mounie headed the resulting corner off target before Hammill curled an effort a whisker wide of goal.
Quaner was again denied by Davies from a quick breakaway.
Substitute Sean Scannell headed against the bar in the final five minutes before Mounie snuck in behind the defence and poked the ball past Davies for the winner.
Barnsley: Davies, Yiadom, MacDonald, Lindsay, Fryers, Hammill, Moncur, J Williams (Mallan half time), Mowatt, Payne (Bradshaw half time), Ugbo (Brown 62).
Unused: Townsend, McCarthy, Jackson, Pinnock, D'Almeida.
Huddersfield: Lossl, Cavare, Zanka, Lowe, Jorgensen, Schindler, Billing (Scanell 72), Hogg, Lolley (O'Brian 83), Ince, Quaner, Mounie.
Unused: Schofield, Williams, Kane, Edmonds-Green.