Bournemouth, chasing an end-of-season play-off place, had been second best for most of the opening 45 minutes but had comfortably held on against a home side badly lacking in attacking ideas.
The visitors began to grow in confidence as the contest wore on, and after star striker James Hayter had squandered a decent opening, Bournemouth bagged all three points thanks to a quality free-kick.
Substitute Marcus Browning took the set piece and delivered an inch perfect 45 yard ball into the path of impressive winger Garreth O'Connor who made no mistake with a controlled right-foot finish into the far corner.
Barnsley's only threat came from on-loan frontman Michael Chopra, who twice went close with long range drives and generally put himself about.
But the rest of the home team were a bitter disappointment to supporters who made their feelings known by booing at the final whistle.
Barnsley did have the ball in the net in the first eight minutes when Australian midfielder Jacob Burns tapped in a low cross from Mick Boulding but the flag was up for offside.
Chopra was then just off target with a low drive from just inside the box, while a firm header from central defender Matt Carbon was well parried by Bournemouth keeper Neil Moss.
The Cherries lost influential defender Eddie Howe through injury just two minutes into the second half, but his replacement Browning proved to be a thorn in Barnsley's side.
He had a good chance on 64 minutes with an attempted lob over Ross Turnbull that was easily claimed by the big Barnsley keeper, but then Browning delivered his free-kick party piece to enable O'Connor to strike the only goal.
Barnsley tried to salvage something, but again Boulding squandered a glorious chance while Chopra was inches away after a clever turn and powerful drive.