George Earthy scored his first goals for Bristol City since joining on loan last summer
Substitute George Earthy scored his first goals for Bristol City as they came from behind to inflict a fifth straight defeat on Middlesbrough and move into the Championship top six.
Earthy, who came on in the 63rd minute, tapped in from close range for his first to draw the Robins level nine minutes later, before adding a second with eight minutes left after Scott Twine's free-kick had hit the crossbar.
Tommy Conway's first-half header had given Boro the lead on his first return to Ashton Gate since making the move to Teesside last summer.
Defeat piles pressure on Middlesbrough boss Michael Carrick, as his side stay 11th ahead of the rest of the Championship's weekend fixtures, while the Robins move into the play-off positions for the first time this campaign.
The win continues Bristol City's strong run of home form, with this their sixth win in their past seven league games at Ashton Gate, while Middlesbrough remain without a win on the road since New Year's Day.
The hosts had an early chance to open the scoring when Twine stepped up for a free-kick after Zak Vyner was fouled, but his effort from distance skimmed over the crossbar.
At the other end Max O'Leary made a couple of saves although neither Neto Borges nor Aidan Morris' efforts seemed to massively trouble him.
The hosts dialled up the pressure and looked more likely to score and Anis Mehmeti seemed to have Mark Travers beaten in the Boro goal, but his left-footed shot in the box trickled narrowly wide of the post.
Sinclair Armstrong then curled a shot that looked like it was going into the top corner, but did not quite dip enough, before Max Bird ran into space and forced Travers into a save.
But the hosts were left to rue their opportunities. First Borges pulled the ball back from the byeline to Delano Burgzorg into space although he scuffed his shot and sent it wide.
Conway did not miss though in the 37th minute after Kelechi Iheanacho darted down the right-wing, cut inside Haydon Roberts and forced O'Leary into a save. The Robins keeper palmed the ball straight to his former team-mate to head in under loud boos from the home crowd.
Tommy Conway turned down a new contract to move to Middlesbrough last summer from Bristol City
Bristol City fans probably rightly felt frustrated that it was not 1-1 at half-time as Bird saw a shot saved and as the ball recycled back Twine, off-balance, sent another effort wide with the last kick of the half.
It was not until Liam Manning made a trip change on the hour mark that the hosts showed signs of drawing level, with Yu Hirakawa, Earthy and Cameron Pring brought on.
All three played a part in the Robins leveller, as Hirakawa crossed from the byeline to Pring, who sent the ball into the box and West Ham loanee Earthy tapped in for his first goal for the club since joining last summer.
Earthy then turned the game on its head in the 82nd minute. Twine stepped up for his second free-kick in two minutes on the edge of the box and, while his shot rocketed off the crossbar, it fell to the 20-year-old for an easy finish into an open net.
'Enjoy the journey, be excited' - reaction
Bristol City manager Liam Manning told BBC Radio Bristol:
"A large percentage of the game the performance was excellent.
"I think if you look at first-half - really good control, pressed really well, lacked quality in and around the box which is what we spoke about at half-time.
"For all the control we find ourselves a goal behind and that was the message second half, keep doing so much of it, add the bit at the end – the ruthlessness, add the composure add the belief that you can do it and credit to the lads because they carried on playing the way we want the second half.
[On the league table] "Let's see what it looks like in 12 [games]. Enjoy the journey, be excited, you want fans to be buzzing about it, and rightly so and I want the lads to be excited about it."
Liam Manning: "Twelve to go..."
Middlesbrough manager Michael Carrick told BBC Radio Tees:
"We've done it too much. We've been ahead in games this season and come away with nothing at the end of it and that's what's hurting us.
"I thought it was understandable the way the start of the second half went.
"I thought they had a bit of the ball but it didn't feel like they were hurting us and were getting frustrated and I thought we defended when we had to, and closed the space off well for the most part.
"The first goal changes a little bit the swing of the game and then the second goal the free-kick that they get is just the totally, totally wrong decision."
