Match ends, Brentford 0, Birmingham City 1.
Birmingham City began life under Spanish boss Pep Clotet with an away victory as they frustrated Brentford in their Championship opener.
Blues defender Kristian Pedersen powerfully headed in the winner against the run of play in the first half, with Birmingham's only notable effort on goal.
Brentford struck the woodwork three times in the first period and controlled possession throughout the game, but could not beat Blues keeper Lee Camp.
Lively winger Sergi Canos went close multiple times for the hosts, who began their final season at Griffin Park with a defeat.
After Birmingham sacked former boss Garry Monk in June, his assistant Clotet was promoted to caretaker head coach and the West Midlands club have said they are "not actively seeking a replacement".
Brentford - who will move to their new Lionel Road Stadium next summer - had not been beaten at home on the opening weekend of the season since 1992, while Birmingham had not opened a campaign with an away victory since 1998.
Thomas Frank's side finished 11th last term, 10 points below the play-off places and eight above the 17th-placed Blues, who were deducted nine points in March for breaching profitability and sustainability rules.
Maupay absent for Bees amid transfer speculation
The Bees gave debuts to defender Pontus Jansson and midfielder Mathias Jensen, with Sweden's Jansson named as captain following his summer move from Leeds United.
But striker Neal Maupay was absent from the hosts' squad, amid reports linking him with a transfer to Premier League clubs including Aston Villa, Brighton, Crystal Palace and Sheffield United.
The Frenchman has scored 37 league goals for Brentford since arriving in 2017.
Ollie Watkins - who has also been linked with a move away from Griffin Park before Thursday's transfer deadline - did start and caused Birmingham plenty of problems, but his first-half effort was tipped on to the crossbar by Camp.
That came shortly before left-back Pedersen headed home expertly from around 15 yards after a good run and cross from 20-year-old Steve Seddon, who was making his first senior competitive appearance for Birmingham.
Clotet also gave a first Blues start to summer signing Dan Crowley, an attacking midfielder, and he was replaced late on by Croatia's Ivan Sunjic, who signed for a reported £6.3m fee in July.
Blues had just 24% of the possession but held out for a victory, capitalising on their only registered effort at goal compared to the frustrated Bees' 15.
Brentford boss Thomas Frank:
"That was quite frustrating. We outplayed them and outbattled them, created four major chances and they did nothing. We had 13 shots, they had one and our keeper hardly touched the ball.
"I hate losing home games, but for me that was one of the best first-half performances in a long time.
"The second half was the disappointing part. We needed to play much quicker, get forward and behind them and we just didn't do that."
Birmingham head coach Pep Clotet:
"It was a very well-organised performance, but we wanted a better display than the one we had, but I don't take away from the effort of the players.
"We didn't manage to challenge Brentford for possession and from the first minute we found it difficult to close a few gaps they were creating. They had great chances, but unfortunately for them and fortunately for us they didn't go in.
"In the first half they deserved more and we deserved less, but when we scored we got more confidence and grew more comfortable.
"It's a good start, but I'm not 100 per cent happy because there were definitely aspects of our play that we need to get better at."
- 23JeanvierSubstituted forZamburekat 81'minutes
- 8JensenBooked at 86mins
- 17MarcondesSubstituted forForssat 64'minutes
- 42SeddonSubstituted forHardingat 58'minutesBooked at 90mins
- 19MaghomaSubstituted forMrabtiat 88'minutes
- 20GardnerBooked at 29mins
- 7CrowleyBooked at 56minsSubstituted forSunjicat 72'minutes
- Gavin Ward
- Shots on Target
Second Half ends, Brentford 0, Birmingham City 1.
Attempt blocked. Marcus Forss (Brentford) left footed shot from the centre of the box is blocked.
Wes Harding (Birmingham City) is shown the yellow card for a bad foul.
Ethan Pinnock (Brentford) wins a free kick in the defensive half.
Foul by Wes Harding (Birmingham City).
Substitution, Birmingham City. Kerim Mrabti replaces Jacques Maghoma.
Mathias Jensen (Brentford) is shown the yellow card for a bad foul.
Foul by Mathias Jensen (Brentford).
Jacques Maghoma (Birmingham City) wins a free kick on the left wing.
Delay over. They are ready to continue.
Delay in match because of an injury Jacques Maghoma (Birmingham City).
Corner, Birmingham City. Conceded by Pontus Jansson.
Substitution, Brentford. Jan Zamburek replaces Julian Jeanvier.
Hand ball by Wes Harding (Birmingham City).
Foul by Julian Jeanvier (Brentford).
Jacques Maghoma (Birmingham City) wins a free kick in the defensive half.
Ollie Watkins (Brentford) wins a free kick in the attacking half.
Foul by Ivan Sunjic (Birmingham City).
Substitution, Birmingham City. Ivan Sunjic replaces Daniel Crowley.