Hulse steered home his first on 32 minutes after Robbie Blake's shot fell into his path and soon after converted Eddie Lewis's cross for his second.
Lewis was involved in the third, it was his shot which Hulse reacted to in predatory style to complete his treble.
Derby manager Phil Brown
"We more than matched them apart from that 12-minute spell
"We suddenly find ourselves 3-0 down and at half-time I was looking at a damage limitation job.
"I could see how fragile our defence was and the confidence started to go. But the players kept going and were rewarded with the goal."
Leeds: Sullivan, Kelly, Butler, Gregan, Crainey (Kilgallon 85), Richardson, Douglas, Derry, Lewis, Hulse (Moore 76), Cresswell (Blake 25).
Subs Not Used: Bennett, Einarsson.
Booked: Butler, Blake, Douglas.
Goals: Hulse 32, 37, 44.
Derby: Camp, Kenna, Davies, Michael Johnson, Whittingham, Bisgaard, Fadiga (Bolder 50), Seth Johnson, Smith (El Hamdaoui 51), John (Holdsworth 51), Peschisolido.
Subs Not Used: Tudgay, Poole.
Goals: Gregan 74 og.
Ref: Graham Salisbury (Lancashire).