Derby have made Butterfield one of their top targets as they look to bolster their midfield options before the transfer deadline on Tuesday.
Huddersfield have rejected several offers for Butterfield with Terriers boss Chris Powell reluctant to lose the all-action midfielder.
However, Derby have come back with an improved offer of £3.5million for Butterfield and Huddersfield have accepted the deal.
Butterfield has now been given permission to hold talks and undergo a medical with Derby ahead of a potential switch to the iPro Stadium
Derby are in the market for midfield reinforcements after losing Will Hughes to a long-term injury, while Craig Bryson is also currently on the sidelines.
Butterfield joined Huddersfield last summer from Middlesbrough in a swap deal with Adam Clayton and he enjoyed a superb debut season at the John Smith's Stadium winning the club's Player of the Season award and his expected departure will come as a big blow to the club.