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.
After the high of Tuesday's dramatic 2-1 win over Middlesbrough when two late goals earned them the three points, this was a real comedown for the Terriers, who struggled to create chances throughout.
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.
Town almost levelled as David Button had to show good reaction to direct Theo Robinson's powerful headed effort away from danger.
Scott Arfield was introduced with 10 minutes left to provide a much-needed creative spark, but it did not come as Huddersfield lost at home for the fifth time this season.