Grant Ward enjoyed a dream debut for Town, scoring a hat-trick as Blues edged a thriller at a sun-drenched Portman Road.
The 21-year-old, who arrived on a three year deal from Tottenham on Monday, entered the fray as a half-time substitute and put Town in front with his first touch inside a minute of the second-half.
Former Blue, Conor Hourihane, levelled the scores immediately for the Tykes but Ward took over the limelight again on the hour, blasting in from 18 yards.
David McGoldrick put daylight between the teams two minutes later when he converted from the penalty spot after Daryl Murphy was brought down in the box.
Barnsley were back in the game though on 72 minutes, Marley Watkins heading in from Hourihane’s excellent free-kick before Ward entered dreamland six minutes from time with a left foot drive from 18 yards that found the net to give him a hat-trick and Town the points in a sensational start to the season.
Adam Webster was handed his debut for Town after joining from Portsmouth in the summer while former Barnsley defender Paul Digby started on the bench, along with fellow newboys Conor Grant and Ward.
The Tykes, fresh from promotion from League One, were forced into a change inside five minutes when Sam Winnall sustained a hamstring injury, Watkins the replacement.
Murphy had the chance to give Town an early lead when Kevin Bru found him down the right but the Republic of Ireland couldn’t find the net under pressure.
Bru then fired just wide from the edge of the box then Teddy Bishop was crowded out as he latched onto a loose ball in the Barnsley box following a corner.
Bart Bialkowski had the first save to make of the game when Tom Bradshaw got on the end of Watkins’ cross, his header straight at the Town ‘keeper.
Adam Hammill curled a right footer just wide on the half hour, then David McGoldrick released Freddie Sears after a long run but the former West Ham frontman couldn’t beat Adam Davies in the Tykes’ goal.
It needed a brilliant save from Player of the Year, Bialkowski to keep Town’s goal intact, the Pole getting a right hand in the way to keep out Bradshaw’s close range effort when a goal looked certain just before the break.
Grant, a loanee arrival from Everton in midweek, and Ward replaced Bishop and Bru at the break and within a minute the signing from Tottenham had put Town in front, beating Davies with a crisp right foot finish from just inside the box.
The lead lasted three minutes. Hourihane, who spent a year at Town before joining Plymouth in 2011, beating Bialkowski from six yards out after Blues failed to clear a corner.
Ward took centre stage again on the hour, Murphy’s cross was cleared to the wideman and he fired it high into the roof of the net.
Two minutes later, Blues had the chance to make it three, Murphy brought down in the box and McGoldrick made no mistake from the penalty spot.
McGoldrick couldn’t find Sears inside the box after robbing Alfie Mawson just outside the box.
McGoldrick threatened again down the left but Davies dealt with his attempted chip comfortably before Barnsley got a lifeline with Watkins heading in from Hourihane’s excellent delivery.
Ward made no doubt who was going to grab the headlines though, becoming the first Town player to score a hat-trick on his debut since a 17-year-old Colin Viljoen bagged three in a 4-2 win over Portsmouth in 1967.