Birmingham will play in Sky Bet League One next season after they were relegated from the Championship despite securing a 1-0 win against play-off contenders Norwich.
Wins for Sheffield Wednesday at Sunderland, for Blackburn at promoted Leicester and for Plymouth against Hull made Blues’ result irrelevant.
This was the fifth time in 11 years that Blues have needed a positive result in their final game of the season but this time it was out of their hands as their 13-year tenure in the second tier ended, despite Paik Seung-ho’s 55th-minute header.
Play was delayed for five minutes halfway through the first half due to a medical issue in a capacity crowd of 27,680 at St Andrew’s.
Birmingham showed the character needed of them at both ends in a bright early start.
Ethan Laird steamed into a challenge on Borja Sainz to win the ball, then Koji Miyoshi forced goalkeeper Angus Gunn to push the ball upwards at the near post after Jay Stansfield’s effort was blocked.
Miyoshi then delayed a first-time shot when unmarked from Lee Buchanan’s cross, before squeezing in a tame, poked effort once he had controlled the ball.
Blues wasted another clear chance when Paik scuffed a poor effort well off target from near the penalty spot from Stansfield’s cross.
Norwich broke through Marcelino Nunez, whose firm low shot was parried away by former Canaries keeper John Ruddy at his near post.
With news that Wednesday had gone 2-0 up, Stansfield’s fierce long-range effort fizzed just wide after a deflection and Laird looped over a header following a corner.
A long ball put Stansfield clean through but he delayed his shot when a lob was on, then Gunn’s reflexes denied Krystian Bielik from point-blank range when Miyoshi’s cross hit him.
Blues fans then howled for a penalty after Sam McCallum appeared to push Miyoshi but referee Oliver Langford waved play on.
Birmingham got the goal they desperately needed when Paik diverted home after Keshi Anderson’s shot as blocked by the sliding Ben Gibson and the ball bounced up for a header.
But with news filtering through of Blackburn taking the lead at Leicester, and Plymouth and Wednesday still winning, it was out of Blues’ hands.
Blues made a double substitution in the 68th minute with Juninho Bacuna and Lukas Jutkiewicz replacing Anderson and Paik.
Jutkiewicz glanced well wide from Laird’s cross as the hosts pressed for a second goal.
With the scores coming through from elsewhere, the atmosphere dropped inside the ground and any momentum from Blues seemed to drain out of the players.
There was a delay while Norwich defender Shane Duffy had treatment for a cut above his eye which allowed a concussion substitute in Danny Batth.
With results elsewhere already in, relegation had already been confirmed before the final whistle, but several hundred Blues supporters still invaded the pitch at full-time.
