The deal could be worth £1.75m as Hulse leaves the Blades with fond memories. Hulse has passed a medical at Pride Park so he completes the switch to United's Championship rivals.
Manager Kevin Blackwell confirmed: "Rob is a decent lad, and we would like to wish him all the best. He will have a better chance of playing first-team regularly at Derby."
Hulse bagged 8 goals in the top flight when with the Blades but had to exit early after a broken leg he suffered against Chelsea at Stamford Bridge. He made a return to competitive action against Cardiff City at Ninian Park in December but has not been able to impress with him scoring zero goals.