Scott Hogan scored for Birmingham City just three days after joining the club on loan from Aston Villa
Scott Hogan scored on his Birmingham City debut as Blues ended high-flying Nottingham Forest's seven-match unbeaten run.
Tiago Silva had put the visitors ahead with his first Championship goal, receiving a headed pass from Joe Lolley on the left before cutting inside a defender to fire into the roof of the net.
Aston Villa loan man Hogan levelled for the hosts in dramatic circumstances - just seconds after Lee Camp had saved a penalty at the other end from Lewis Grabban following the goalkeeper's foul on Ryan Yates.
Former Villa man Grabban, looking for his 17th goal of the season, went on to see a shot on the turn hit the crossbar and another second-half effort cleared off the line by Harlee Dean.
Kristian Pedersen won it for Blues, bundling the ball home from a corner to consign the Reds to a defeat that drops them to fourth in the table.
Forest, looking to end a 21-year absence from the Premier League by winning promotion to the top flight for the first time in the 21st century, were leapfrogged by Fulham after the Cottagers overcame Huddersfield. The defeat leaves them four points adrift of the automatic promotion spots, with Leeds now second after their defeat by Wigan.
Blues, who had taken just two points from a possible 21 at home since 9 November, move up to 17th.
Forest almost gifted Blues an early lead in calamitous style, when goalkeeper Brice Samba's attempt to roll the ball out found Lukas Jutkiewicz on the edge of the area. Samba and Ben Watson, however, scrambled to put pressure on the forward, who was eventually denied by a block from Joe Worrall.
Minutes later, Portuguese midfielder Silva put Forest ahead with what was just his second goal in English football - his first having been the winner against League One side Fleetwood in the League Cup in August.
Tiago Silva (left) netted his first Championship goal for Forest
Camp was not troubled again until Grabban stepped up to the penalty spot but, although he saved, Blues quickly countered and Jeremie Bela crossed for Jutkiewicz, who knocked the ball down at the far post for Republic of Ireland international Hogan to tap home from close range.
Both sides had gilt-edged chances to take an early second-half lead, Jutkiewicz sending a free header from a Josh McEachran cross wide before Grabban hit the bar on the turn from close range.
Just a minute after Grabban saw another shot cleared off the line, Bela tested Samba with a fierce first-time shot.
The action remained end to end as both sides chased all three points before the game was decided by a scrappy effort from Pedersen, which crossed the line amid loud protests for a foul.
Birmingham City head coach Pep Clotet told BBC WM 95.6:
"Forest had some control in the middle of the first half and we had to do a lot of good defending, but offensively we found the spots we wanted to find.
"Despite losing 1-0 the team was very focused. Campy made that save from the penalty and then, after Scott Hogan's goal, the team got back in at half time in a good position.
"We talked about how we could hurt them a bit more, and the players shared their thoughts as well.
"As a group, we managed the second half very well and were very dangerous on the break. I would say we deserved the win, which is very important for our fans."
Nottingham Forest manager Sabri Lamouchi told BBC Radio Nottingham:
"I am very disappointed because we started the game in the right way. We score, we play well.
"The penalty changes many things. You can score and close the game. We finish 1-1 at the end of the first half and the second half was just unbelievable.
"I'm just so upset, disappointed, because we give them the three points. Congratulations for Birmingham, but we gave them everything.
"From the beginning to the end, three points, easy. We need more character to close the game because it was in our hands. We controlled the game until the penalty."
