Nathan Broadhead and George Hirst netted goals just before the break to give the Blues a crucial 2-0 half-time lead over Barnsley at Oakwell.
Town, with 5,000 fans backing them behind the goal they defended in the first half named the same side which beat Peterborough 3-0 at London Road on Saturday.
Former Blues striker James Norwood started for the Tykes, who still have a faint hope of an automatic promotion spot, while ex-Town full-back Barry Cotter and one-time loanee Luke Thomas were on the bench.
Town started on the front foot, Broadhead cutting an early ball across from the left. But it was the Tykes who hit the first shot of the game, Nicky Cadden’s cross from the left reaching Jordan Williams out wide on the right but his shot flew into the Town fans, much to their delight.
Hirst was shown the first yellow card of the match in the ninth minute for tripping Williams as the home side looked to break following a Town attack, which seemed more than a little harsh, particularly as a Norwood challenge on Leif Davis moments early hadn’t been similarly punished.
The game had started in a frantic cup-tie-like manner but with the Blues looking the more dangerous.
And in the 11th minute, they went very close to going in front. A Broadhead cross from the right was half-cleared to Davis on the left and the full-back played it inside to Massimo Luongo, who curled a shot beyond Tykes keeper Harry Isted but off the bar.
The South Yorkshiremen subsequently had a spell in charge and on 16 Norwood hit a low shot from outside the box which was easy for Town keeper Christian Walton.
Five minutes later, the ex-Blues striker sent a dangerous ball over from the left but beyond striker partner Devante Cole.
On 24, a corner from the right was headed out by skipper Sam Morsy to Adam Phillips, whose shot took a deflection but still looped comfortably through to Walton.
Moments later, Jon Russell became the first Barnsley player to get his name in the book for a foul on Morsy as Town broke.
Town had been more frantic than composed in their approach, looking to get the ball forward quickly with Barnsley having more possession.
But in the 33rd minute, the Blues again went close to going in front via the best chance up to that point.
Chaplin flicked inside to Broadhead on halfway on the right and the Wales international brilliantly threaded in Hirst but the on-loan Leicester striker screwed his shot across the face, the ball curling away and out for a throw.
Town were starting to control the game and play their flowing football and in the final minute of the half won their first corner.
And from the flag-kick, they went in front. Davis hit a powerful ball to the near post and Broadhead flicked a header in between keeper Isted and his post.
It wasn’t initially clear that the ball had gone in rather than nestling in the side-netting but once the players began celebrating a huge roar erupted from behind the goal at the other end.
The Oakwell PA announced two minutes of injury time and within a minute, the Blues made it 2-0.
Hirst battled with home skipper Mads Andersen a third of the way inside the Barnsley half on the left, then took the ball towards the Barnsley penalty area under pressure from three players.
The former Sheffield Wednesday youngster appeared to deliberately allow the ball to drift behind him to create space before lashing a superb strike into the top corner of the net to send the fans at the opposite end wild once again.
Norwood headed a free-kick wide at the near post for the shell-shocked Tykes before referee Ben Toner’s whistle signalled another big roar from the 5,000 fans and chants that ‘The Town are going up’.
And sing they might, the Blues having gone a long way towards picking up the five points they need to secure an automatic promotion place.
The half had started in a cup-tie like manner with the game not always suiting the Blues’ usual approach.
However, while Barnsley had had spells on the ball, Town had got on top by the end of the half and had come close twice before their late-half double, while Walton hadn’t been forced into a serious stop.
Town look to have done the hard work in the first half and now need to see the second period out to claim a vital three points.
Barnsley: Isted, Williams, Russell, Kitching, Andersen (c), Cadden, Kane, Norwood, B Thomas, Phillips, Cole. Subs: Collins, Benson, L Thomas, Cotter, Larkeche, Tedic, Watters.
Town: Walton, Clarke, Woolfenden, Burgess, Burns, Morsy (c), Luongo, Davis, Chaplin, Broadhead, Hirst. Subs: Hladky, Leigh, Ball, Edwards, Harness, Jackson, Ladapo. Referee: Ben Toner (Lancashire).