The win made it nine games unbeaten in Yorkshire for the Town, dating back to three days short of two years, as Nathan Jones' side managed the game plan to perfection after summer signing Bell's fourth-minute strike.
Manager Jones made five changes from Saturday's 3-2 defeat at West Brom, with Peter Kioso making his first league start for the Hatters, whilst there was a return to the starting eleven for the first time since February for Tom Lockyer alongside him in a three-man central defensive unit, with captain Kal Naismith on the left.
Henri Lansbury – who played 45 minutes at the Hawthorns – started in midfield with Pelly-Ruddock Mpanzu, whilst Admiral Muskwe and Cameron Jerome also came in to accompany Elijah Adebayo as part of a front three, Muskwe playing in the hole.
The Hatters made a dream start when Bell fired them into a fourth-minute lead. Lansbury played the ball up the right, Adebayo crossed low, missing strike partner Jerome out, and left-back Bell raced onto it and cracked a right-footed shot low past Tykes keeper Brad Collins.
Former Barnsley player James Bree spurned a chance to double the advantage on 13 minutes. After Adebayo had challenged Collins for an aerial ball on the left edge of the area, Muskwe collected and crossed, with the hosts' header clear only going as far as Bree on the 18-yard line, but the right-back's mis-hit volley was well wide.
Lansbury arced a 21st-minute free-kick into the Barnsley six-yard box, but Adebayo couldn't wriggle free of his marker to get any purchase on his attempt to divert it past Collins.
Seconds later, Simon Sluga was quickly off his line to deny Romal Palmer when the Tykes' midfielder burst into the box, the Town keeper was equally dominant coming through a thicket of players to punch the resulting corner clear.
Lockyer produced a perfectly timed sliding challenge on the edge of the Town six-yard box to deny Clarke Oduor a golden chance of an equaliser, then Toby Sibbick did likewise, twice in quick succession, in the Barnsley penalty area to prevent Muskwe doubling the lead, the first going behind for a corner, the second collected by a grateful Collins.
Muskwe had made an enterprising start in the number ten role, and it was his dribble in the final third that created the Town's next opportunity on 33 minutes, setting Jerome free into the area to cross low, looking for Adebayo, but the former Walsall man couldn't quite get to the ball as it ran acoss the six-yard box.
Sluga was at his brilliant best three minutes later to dive low to his right and push a Callum Brittain shot away, Kioso sliding in to hook the loose ball away as the Barnsley midfielder looked to pounce on his own rebound.
Then Michal Helik was quickly the first player into ref Oliver Langford's notepad for illegally halting Adebayo's run down the right wing, after Bree had fed the striker with a measured ball along the touchline.
Josh Benson was the next home player to go close to an equaliser, somewhat fortuitously, as Pelly-Ruddock Mpanzu slid in to challenge on the edge of the Hatters' box and the ball ricocheted just wide of Sluga's right post.
Then Muskwe became the first Town man to be shown a yellow card, for a foul on Palmer, soon joined by Adebayo for delaying a Barnsley free-kick after he was incorrectly flagged offside.
The Hatters came quickly out of the blocks again after half-time, Jerome almost getting in behind within seconds of the restart, only for Sibbick to make a crucial challenge as he looked to advance on Collins' goal.
But it was Barnsley who created the first chance of the second period, Brittain angling a low drive across Sluga but safely wide of the far post from a Hatters perspective.
Adebayo stole a march on the Tykes' back four just before the hour, in an almost identical position to the one Jerome found himself in, but after latching onto Bree's throughball, dragged his shot wide of Collins' right-hand post.
Brittain was proving a handful down the Barnsley right and he slid another ball across the Town six-yard box, again unanswered by his team-mates, before the magnificent Lansbury called Collins into action at the other end, the Barnsley keeper needing to be at his best to push the midfielder's powerful half-volley away for a corner.
Barnsley midfielder Benson shot over from the edge of the box with just over 20 minutes to go, as Jones prepared to make his first change of the evening, bringing Harry Cornick on for Jerome, who left the field to rapturous applause from the travelling Town fans.
Sluga made another good save in the 73rd minute to keep a 25-yard shot from Callum Styles out. Captain Kal Naismith then did well to get a glancing header on Liam Kitching's cross, before Muskwe threw himself in the way of a piledriver from Brittain to protect the Town's lead.
Barnsley sub Devante Cole looked to have got away from Kioso with 13 minutes left, but the Town man raced back to produce another brilliant sliding tackle in the box, before helping see the danger off from the resulting corner.
The Hatters survived a scare in the 87th minute when Styles volleyed over from 15 yards, with Jones replacing Lockyer - who lasted 87 minutes on his return from injury - with Gabe Osho and Muskwe with Glen Rea, just before six minutes of added time were announced.
Goals:
Town - Bell (4)
Attendance: 12,299 (748 Hatters)
