Callum Harriott's early strike - in what was just his second start - won the game for the Addicks, who picked up their eighth away win of the season.
Bristol City's win over Middlesbrough means Huddersfield are just five points clear of the npower Championship relegation places, while their goal difference of minus 25 makes for grim reading.
After three minutes Charlton were ahead. A short free-kick from Chris Solly on the left of the area found an unmarked Harriott, who fired past Alex Smithies and into the corner.
It was a sluggish start from Huddersfield and it was not until the 15th minute when they created their first decent opportunity when Oscar Gobern's near-post header went wide.
Town were starting to have more of the ball and after 27 minutes they almost levelled as David Button had to show good reaction to direct Theo Robinson's powerful headed effort away from danger.
Charlton always looked dangerous on the break and Danny Haynes should have at least tested Smithies with a header from Lawrie Wilson's cross.
The striker did however force a good save from the stopper seconds later. Harriott raced through the Huddersfield midfield and his excellent through ball found Haynes, who struck a decent effort to Smithies' right with the keeper pushing his effort to safety.
Charlton were now creating chances at will and Wilson's near post flicked header from a Johnnie Jackson free-kick was cleared off the line by a stretching Peter Clarke.
In added on time, Oliver Norwood's swerving effort had Button in trouble, but he managed to claw the ball away to safety. With Huddersfield struggling to get the ball to stick up front, Robins decided to act.
He brought on strikers Alan Lee and Danny Ward - who both scored against Boro on Tuesday - for Robinson and Norwood after 55 minutes, with Clayton moving into the middle as Town went 4-3-3.
Midfielder Dorian Dervite replaced striker Ricardo Fuller after 66 minutes as Chris Powell looked to repel Huddersfield's pressure. The extra defensive cover worked as Huddersfield could not break down the visitors.