Sharp, on loan from Southampton since September, headed in on 32 minutes and it proved enough to secure the points for the Royals.
Huddersfield created chance after chance but were short on fire-power with 12-goal top scorer James Vaughan out with a thigh injury - and they finished with 10 men after Joel Lynch's late dismissal.
Winger Adam Hammill fired straight at Reading keeper Alex McCarthy from Oscar Gobern's pass on 18 minutes.
A minute later left-back Paul Dixon beat opposite number Chris Gunther and then turned inside Alex Pearce only to blast wide.
Martin Paterson scooped a shot over the bar when unmarked after Hammill's cross fell to him off a defender.
A defence-splitting pass from Oliver Norwood went through Patterson's legs and was then miscontrolled by the unmarked Danny Ward on 24 minutes.
Norwood also set up Gobern, who shot straight at McCarthy from the edge of the box four minutes later.
Reading, missing seven key players through injury or suspension, soaked up the pressure and then hit Huddersfield on the break.
Kaspars Gorkss headed wide from a Jordan Obita free-kick in the first minute, but the Royals did not created another chance until Sharp scored.
Pavel Pogrebnyak's byline cross gave Sharp his chance and though Terriers keeper Alex Smithies got a hand on the downward effort, he only succeeded in palming the ball into the roof of the net.
Sharp, who scored on his full debut against Charlton two weeks ago, also went close six minutes later.
He drilled wide on a breakaway after referee Oliver Langford twice gave the visitors advantage despite fouls against Pogrebnyak and Royston Drenthe.
The second half continued in the same vein, with a Ward shot blocked by Gunther and a long-range Lynch effort well held by McCarthy.
Ward forced McCarthy into another good save on 65 minutes and then Norwood fired over from a Hammill cross when unmarked.
Paterson summed up Huddersfield's afternoon when he hit the base of the post on 74 minutes when also unmarked from Dixon's clever cut-back.
Drenthe went close in the second half for Reading, who have now won three of their last four games.
Chances came at either end late on, with Town substitute Sean Scannell firing straight at McCarthy from distance from Ward's pass.
Pogrebnyak dispossessed Lynch on 88 minutes and was only denied the clincher by Anthony Gerrard's last-ditch goal-saving block.
Scannell then headed wide from close range from Ward's cross in stoppage time, with home fans and players claiming a corner that was not given.
Town's frustration was completed in the fourth minute of added time when Lynch, booked on 87 minutes, was sent off for a second yellow. He fouled Pogrebnyak both times.