Goals from Scott Hogan and Przemyslaw Placheta gave Birmingham their first win under new boss John Eustace and continued Huddersfields poor start to the season.
Striker Hogan put the hosts ahead after five minutes with a superb diving header from Juninho Bacunas cross.
And Polish winger Placheta scored just before the interval - his first goal since arriving on loan from Norwich last month.
Danny Ward pulled one back in the second half but the visitors were unable to find an equaliser.
Huddersfield, beaten by Nottingham Forest in last seasons Championship play-off final, have now lost both their games under new boss Danny Schofield, who took charge after Carlos Corberan resigned in July.
It has been a tough summer for the Yorkshire club, who have also lost key players Harry Toffolo and Lewis OBrien since their Wembley defeat - both to Forest.
They were disjointed in the opening 45 minutes and the second goal came as a result of some dismal Terriers defending.
After Tom Lees was caught out by a ball over the top, Hogans cross was overhit but still found both Jordan James and Placheta unmarked at the far post.
James effort was blocked and Plachetas follow-up was weakly palmed into the net by keeper Lee Nicholls, who should have done better.
Schofields side were much better after the restart and reduced the deficit just after the hour mark when a slick move culminated in Sorba Thomas finding Ward, who fired home.
They then put Birmingham under pressure - and had appeals for a late penalty ignored when Jordan Rhodes went down in the box - but Eustaces team held on.
Match ends, Birmingham City 2, Huddersfield Town 1.
Second Half ends, Birmingham City 2, Huddersfield Town 1.
Foul by Duane Holmes (Huddersfield Town).
George Friend (Birmingham City) wins a free kick on the left wing.
Corner, Birmingham City. Conceded by Lee Nicholls.
Attempt saved. Auston Trusty (Birmingham City) left footed shot from the left side of the box is saved in the bottom left corner. Assisted by Juninho Bacuna.
Attempt saved. Juninho Bacuna (Birmingham City) right footed shot from the centre of the box is saved in the centre of the goal. Assisted by Jordan James.
Oliver Turton (Huddersfield Town) wins a free kick in the defensive half.
Foul by Auston Trusty (Birmingham City).
Substitution, Huddersfield Town. Josh Koroma replaces Jack Rudoni.
Substitution, Birmingham City. George Friend replaces Przemyslaw Placheta.
Foul by William Boyle (Huddersfield Town).
Lukas Jutkiewicz (Birmingham City) wins a free kick in the attacking half.
Foul by Jack Rudoni (Huddersfield Town).
Jordan Graham (Birmingham City) wins a free kick in the defensive half.
Substitution, Birmingham City. Lukas Jutkiewicz replaces Scott Hogan.
Foul by Jordan Rhodes (Huddersfield Town).
Dion Sanderson (Birmingham City) wins a free kick in the defensive half.
Attempt blocked. Jordan Rhodes (Huddersfield Town) right footed shot from the centre of the box is blocked. Assisted by Sorba Thomas.
Offside, Huddersfield Town. Duane Holmes tries a through ball, but Sorba Thomas is caught offside.