Billionaire owner Michael Ashley watched his first game at St James' Park wearing a United top and was left punching their air in delight when Michael Owen broke the deadlock just before the hour mark.
And to cap an excellent night for the Geordies, Obafemi Martins, who had just replaced Owen, made it safe with a second four minutes from time.
Owen made only his 14th start for Newcastle, just two days short of his second anniversary of becoming a United player following his move from Real Madrid, partnering Shola Ameobi up front in a much changed side.
And it was Owen who created the first chance on the quarter hour mark when he broke on the left and hit a drive that Heinz Muller could only parry into the air before gratefully holding on to the rebound.
Nobby Solano then had a 25-yarder deflected behind and Charles N'Zogbia suffered the same fate after 33 minutes.
Barnsley's first effort on goal came seven minutes before the break direct from a free-kick with the fit again Shay Given pushing away a 25-yard effort from German defender Dominik Werling.
Just before the break N'Zogbia had another shot turned behind and then Muller was a relieved keeper when he punched a clearance against Owen, but managed to grasp the goalbound rebound.
It took 12 minutes of the second half to break the deadlock with the new-look striking partnership combining to finally break down the rugged Barnsley rearguard.
There's nothing Owen likes better than to run on to an inch-perfect through ball and when that was supplied by Ameobi, the little striker struck his first goal at St. James' Park since December 2005 and his eighth in the Newcastle colours.
Newcastle were almost caught out by a fluke after 63 minutes when Barnsley skipper Robert Kozluk whipped in a right-wing cross that Given could only watch as it crashed to safety off his far post.
Ameobi again showed silky skills when playing the ball into the path of substitute Nicky Butt, who advanced to the edge box only to show his lack of finishing prowess by screwing his effort hopelessly wide.
Owen made way for Martins in the 83 rd minute and the latter showed his trademark somersault three minutes later by making the tie safe with his third goal of the season.
There was a hint of handball when he controlled a deep right-wing cross, but the finish was clinical as he added to his two opening day strikes at Bolton.
Outstanding Tykes defender Werling was cautioned for voicing his disgust at over-fussy referee Graham Salisbury over the handball situation.