In an anxious opening 45 minutes Scunthorpe enjoyed the majority of the play but struggled to create much in front of goal.
Huddersfield, in their first match under new manager Andy Ritchie were well organised, but also lacked much threat in front of goal.
It was at the start of the second half that Scunthorpe began to crank up the pressure though they had an anxious moment in the 55th minute when striker Luke Beckett netted from close range for the visitors, only to be flagged off-side.
At the opposite end Jermaine Beckford missed a glorious chance to open the scoring for Scunthorpe when he headed wide with the goal at his mercy.
Beckford volleyed another chance just over while a free-kick from Neil MacKenzie whistled just passed the angle.
But Scunthorpe finally made the breakthrough in the 68th minute when Huddersfield keeper Matt Glennon could only parry a shot from Kevan Hurst and Sharp was on the spot to force home the rebound.
Sharp struck again with his 30th goal of the season when he converted from the penalty spot in the 83rd minute.
It came after his own cross from the right had been handled just inside the area by Huddersfield full-back Joe Skarz.
At the final whistle there were scenes of wild jubilation from the Scunthorpe fans as they celebrated their second promotion in three seasons and a return to Championship level for the first time since 1964.