Marley Watkins put Barnsley ahead before Florian Jozefzoon equalised for the visitors, who also missed a penalty when Jota’s effort from the spot was saved.
The visitors had the first effort of the game when Lasse Vibe laid the ball off to Jota on the edge of the area and he put his low shot wide.
Barnsley responded with a chance of their own when Ryan Kent’s cross from the left was met by Watkins, who put his near-post header wide.
As the home side began to gain the upper hand, Gethin Jones had an effort on target but he failed to get any power behind his shot and the ball trickled into the grateful arms of keeper Jack Bonham.
Vibe, who had been hurt in a challenge, played on briefly after receiving treatment before being replaced by Sergi Canos.
Bonham was called into action to keep out Tom Bradshaw’s long-range effort before Barnsley opened the scoring.
The goal came when Josh Scowen’s cross picked out Watkins, whose effort found the net with the aid of a deflection.
The hosts threatened to extend their lead but Bonham redeemed himself, saving from Scowen after dropping the ball.
Jozefzoon equalised four minutes before half-time, slotting the ball past Adam Davies after receiving a fine through-ball from Jota.
Brentford were awarded a 47th-minute penalty when a Canos shot was blocked inside the area by Angus MacDonald but Jota’s spot-kick was superbly saved by Davies, who turned the ball onto his left-hand post.
It was end-to-end action, with George Moncur’s low drive turned wide while Brentford responded with a Canos header coming back off the bar.
Moncur then shot over and at the other end, Konstantin Kerschbaumer’s effort went wide.
Bradshaw had a great chance when he was put through on goal by Scowen, only to be denied by a brave block from Bonham.
Just before the hour mark, Moncur rattled the bar with a thunderous strike following good work from Kent.
The impressive Scowen, whose creative flair caused problems for the visitors all afternoon, saw his floated free-kick hit the side-netting.
Barnsley continued to carve out openings and there was a great opportunity for Watkins, who chipped over with a clear sight of goal. He also saw a rasping long-range effort clear the bar shortly afterwards.
It was not all one-way traffic, however, as Davies had to keep out a low shot from Canos.
Matty James twice went close for the hosts in the closing stages, firstly heading narrowly wide and then seeing Bonham making a good save to tip his shot over.