Lee Novak notched his 13th of the season with a hooked finish and Jordan Rhodes smashed in his 34th of the campaign before half-time.
Chesterfield had matched Huddersfield for 20 minutes before they were rocked by two quality finishes that put Simon Grayson's team in charge.
Novak sent a right-foot volley from just outside the area inside Tommy Lee's right-hand post in the 23rd minute, before Rhodes swivelled to drive in Jack Hunt's raking cross four minutes later.
Rhodes pulled a shot wide and Gary Roberts also hit the bar before the break, and although Chesterfield pushed Huddersfield back in the second half the visitors' grip on the game was never really threatened.
