Jacob Mellis was the difference between these two sides in a game that should have been more comfortable than it was for the home team. The ex-Chelsea man headed a home a superb cross from Martin Cranie in the 50th minute which kept up Barnsley's 100% home record, but that wasn't the main talking point; a two-footed lunge from Bobby Hassell on Bristol's Jon Stead reduced the home side to ten men, but that didn't matter in the end as a resilient performance in the second half gave the points to Barnsley.
On the back of conceding eight goals in two league games, Barnsley fought through late forward surges from a determined Bristol side who were in contrasting form going into this game, having scored eight in their previous two league outings.
Barnsley started the game very nervously and it was evident for everyone to see - both Ben Alnwick and Chris Dagnall dawdling on the ball resulting in losses of possession.
Bristol had the better of the opening five minutes, carving out several chances but never really tested Alnwick, looking to redeem himself from his red card on his debut.
More uncertainty about the new goalkeeper on six minutes as his poor clearance led to another Bristol chance but this time the Barnsley defence were quick to close down, causing Albert Adomah to aimlessly hoof the ball over the top in hope, but to no avail.
The home side were - against Keith Hill's style of play - resorting to the long ball up to 6' 2" marksman Craig Davies to try and create some chances to break the deadlock but there were no signs of Bristol's defence letting anything through anytime soon.
Another error in Barnsley's back line seven minutes in - this time from stand-in captain Scott Wiseman - allowed Stead to turn and unleash a tame curling effort but his deflected shot rolled harmlessly into the grateful arms of Alnwick.
Bristol continued to attack and were dominating the game until Tomasz Cywka dribbled his way down the centre of the pitch before sending the ball out to his left to find Davies in acres of space, and the Welshman let fly with a bending effort that cannoned back off of Thomas Heaton's left-hand post to Mellis whose scuffed attempt ricocheted wide for Barnsley's first corner of the game.
The tide of the game was beginning to turn in Barnsley's favour, and they started to pile on the pressure with two threatening corners being met by Stephen Foster's headers but the away defence dealt with them comfortably.
Pinball in the Reds penalty area on 13 minutes created a half-chance for Bristol, but the ball wouldn't drop for Martyn Woolford, as Alnwick got down well to smother it and avert any danger.
Any attacks down the left wing for Bristol were always cut out by the tremendous Cranie on his home debut - a solid performance from the Coventry old boy went down brilliantly with the vocally strong crowd on Saturday.
A quarter of an hour into the match and appeals from Barnsley fans for a penalty for handball went unheard when Davies' strike appeared to have hit Bristol City defender Louis Carey on his lower arm.
Having come closest to opening the scoring, Barnsley pushed on to try and find this important first goal and as hard as they tried, they didn't succeed. They again came close just before the 2o minute mark when Mellis' lofted ball into the box was cleared out to Hassell who beat two players, passed to Dagnall on the right-hand side of the area, and the 26 year old's snapshot was well saved by Heaton after a neat turn on the edge of the box.
The resulting corner caused havoc in the Bristol penalty area and some slack movement from Adomah allowed Cranie to win possession and play a neat little ball out to Mellis who blazed his effort way over the bar. The signs were positive and Barnsley were getting closer.
Midway through the first half and the Reds were firmly on top of this encounter now, breezing forward with ease and troubling Bristol's defence with any chance they got - Cywka brilliantly working his way away from Woolford before chipping a lovely ball to the far post but unfortunately no one was there to head home this crisp cross and the ball was nodded away by Carey.
Sloppy play from Mark Wilson a minute later gifted the ball to Davies and he drilled a 25 yard shot low and hard but it was straight down the centre of the goal and into the thankful arms of Heaton.
Barnsley came their closest yet to getting on the score sheet when Cywka found space on the edge of the area and dinked a lovely ball on to the head of Davies and his downwards header was palmed away superbly by Heaton and the ball was then deterred from all danger as Adomah hacked the ball high upfield.
A nifty run from Dagnall just before the half hour point allowed him to play in a low ball but his cross bounced off the leg of Cywka - nothing the Pole could do about that.
Barnsley were fully into their stride now and were creating chances galore, Cywka and Mellis being at the forefront of every Reds attack and some great vision from both played in Davies on two occasions but the striker failed to conjure up a goal. Mellis was then played through by a terrific ball from Stephen Dawson but he fired his attempt inches wide of Heaton's left post.
The away side had time to regroup in the five minutes that followed and looked to be holding off Barnsley's forceful attacks well until Dagnall squirmed into the box and laid the ball off to Davies whose quick-fire shot sparked half-hearted appeals for a penalty for handball from the Barnsley faithful, but the referee wasn't having any of it.
Some excellent passing and movement from the whole midfield line and full backs five minutes before the interval allowed the Reds to work their way into space and Mellis further bettered his already fantastic performance by sliding the ball into Dawson who flicked it up and struck his left-footed volley into the ground. The ball was destined for the bottom corner but Heaton got down well to grasp it.
Barnsley came even closer to breaking through on the stroke of half time - Cywka playing a sweet ball through the middle for Dagnall to run on to but the striker was just beaten to the ball by Heaton who collected it whilst receiving a blow to the head due to Dagnall's momentum causing him to collide with the Bristol number one.
The second period kicked off and Bristol City brought on Marvin Elliott for the ineffective Adomah to keep up with Barnsley's packed midfield - the winger struggling to cope in his unnatural position of central midfield.
Five minutes into the second half and the Reds got that breakthrough they so thoroughly deserved - Mellis planting his header on to the underside of the crossbar and in after a magnificent cross from Cranie.
Things took a turn for the worst only a minute after the goal as Hassell's rash foul was deemed to be worthy of a red card by referee Steve Rushton. The full back went in high on Bristol striker Stead and could have no complaints after being given his marching orders.
That sending off opened up a portal for Bristol to get back into the game but Barnsley were not to be pushed over and held a tight defensive line as Bristol struggled to show any real penetration.
Bristol came their closest yet when pinball madness in the penalty area resulted in the ball bouncing to Sam Baldock nine yards out, but the £1m+ man could only find Alnwick's gloves when under intense pressure from the home defenders.
This chance sparked a flurry of attacks from the away side but Barnsley were holding their own with only ten men - Cole Skuse the first to try his luck but his effort from distance was well blocked by Wiseman.
With an hour of the match surpassed Barnsley brought on teenage prodigy John Stones for goal scoring hero Mellis, and also introduced Marlon Harewood who replaced the impressive Davies - This made something click and the Reds were suddenly in the ascendency again.
Despite Barnsley's dominance so far, some good link up play from Stead and Woolford - combined with poor keeping from Alnwick - allowed the Bristol winger to nip in behind the 'keeper and with only Stones on the line, Woolford's header brought an outstanding block from the 18 year old local lad - however, the ex-Scunthorpe maestro really should have equalised.
Bristol brought on Ryan Taylor on 67 minutes in place of new-boy Baldock to try and find a goal to level the scores.
The sending off of Hassell meant Barnsley had to resort to a deep defensive line and the Robins were finding it difficult to pierce through this stubborn back four, having to alternate to long shots instead of trying to writhe and wriggle their way through.
Another half-chance for the visitors with 20 minutes remaining on the clock - this time a whipped cross over to the back post meant substitute Elliott was always stretching to get a good connection and his slight touch sent the ball behind for a goal kick - relief for Barnsley.
Bristol brought on more attacking strength on 73 minutes when Steven Davies - recently signed from Derby - replaced midfielder Stephen Pearson, and Davies was involved in the action straight away. Greg Cunningham played a 40 yard pass right on to the penalty spot and as Alnwick came out, flapped, and completely missed the ball, Davies only managed to steer his header wide when he should have done better.
The instrumental Cywka was trying his luck again with 77 minutes gone as he dispossessed Davies, ran at the visiting defenders and fired wide from 25 yards when he had options either side in Harewood and Dagnall.
The Reds were persistent and kept darting forward whenever possible - Dagnall and Cywka doing extremely well on several instances and showing true grit, determination, and that never say die attitude.
Bristol came closer yet - Davies again heading an inch wide of Alnwick's right-hand side post when he should have done better, and despite having the man advantage, the away side were on the back foot for most of the remaining ten minutes after Harewood and Dawson broke through the Bristol back line with some energetic bursts of football.
Barnsley very nearly doubled their lead with the clock ticking over into injury time as Stones steamed forward and curled a lovely ball around the away team's centre back that landed at Harewood's feet but the striker just couldn't get any power behind the shot and the covering defender got back to clear the ball off of the line and into Heaton's appreciative arms.
Bristol struck the bar in the 91st minute through Davies as his free kick thundered past a stranded Alnwick in goal - an equaliser would have been harsh on Barnsley who had been the better side for long periods of the game and had shown fantastic resilience after going a man down.
Barnsley did everything they could to keep the ball in the corner to run down the timer and intelligent play from the remarkable Harewood allowed him to convince the away defenders he was going to the corner before quickly shifting his path inwards and bearing down on goal, and from a tight angle he couldn't beat Heaton in the City net.
Full time at Oakwell and the final score finished Barnsley 1-0 Bristol City.
Jacob Mellis heading home the winner.
Ben Alnwick - 6 - Poor distribution from the keeper and tended to flap at everything. One decent save in a below par performance.
Martin Cranie - 9 - A phenomenal performance from the new boy. He adapted extremely well in various positions and supplied a marvellous cross for the winner.
Scott Wiseman - 8 - Looks to be finding his feet now he's being played at central defence, and despite a shaky start, looked commanding at the back and made some crucial blocks.
Stephen Foster - 7 - Assured as always and had a couple of chances in the first half. He seems to be past his best Oakwell days now but is still always a reliable player at the back.
Scott Golbourne - 7 - Great going forward and has a lot of flair for a defender but does have a tendency to get caught out and is more than often having to track back.
Bobby Hassell - 7 - Decent up until the sending off, which was unlikely for a man of his experience. Was the heart of a few attacks in the first half too.
Stephen Dawson - 8 - Seemed to be carrying the team when they needed it after the dismissal. Could be an ideal captain as his communication is second to none.
Tomasz Cywka - 9 - Man of the match and deservedly so. A magnificent performance and some amazing footwork that could only have been topped off by a goal.
Jacob Mellis - 9 - Played his role brilliantly until he was subbed off. Took his goal well and created a fair few chances and could very well turn out to be better than the old Jacob, we'll see.
Chris Dagnall - 9 - After coming under recent criticism, he may well have silenced doubters with an amazing performance that warranted a goal. Sublime work rate and never gives up.
Craig Davies - 8 - Fantastic hold up play from him and was very unlucky not to grab a goal after he hit the post. This could be a great season for him.
John Stones - 8 - Outstanding. That clearance may well have won the points for Barnsley and he never stopped going until the final whistle. A few misplaced passes but that'll go with experience.
Marlon Harewood - 8 - Came on to do a job and did that job, and did it very well. His hold up play mirrored Davies' and his strength was vital when it came to keeping the ball in the corner.