Pablo Counago nicked the ball off Claude Davis to open the scoring and Jon Walters pounced on a Darren Powell error to seal the points.
Derby rarely threatened and only forced one meaningful save from Richard Wright all afternoon when he superbly beat away sub Przemyslaw Kazmierczak's firm header.
Darren Ambrose, who is back at Ipswich on loan, had the first clear chance of the game on seven minutes when he had a free header from David Wright's cross, but sent it straight at Roy Carroll.
Alex Bruce volleyed over from an Owen Garvan corner and Ambrose forced Carroll to palm a low 20-yard drive around the post.
Carroll saved a fierce David Norris drive but he was beaten on 27 minutes when Counago beat Davis to a Walters flick-on and coolly slotted into the corner.
Rob Hulse shot wide on the turn and Miles Addison's deflected shot forced a diving save from Richard Wright as Derby tried to hit back.
Ipswich continued to dominate after the break and Walters should have scored when he raced on to a Garvan through ball but he dragged his shot wide.
Derby missed a great chance to equalise when Nacer Barazite crossed for Kazmierczak to force a fine save from Wright, but three minutes later Town doubled their lead.
Ipswich comfortably saw out the remaining quarter of the game and could have won more easily but for good Carroll saves to deny Norris and sub Kevin Lisbie.
Sub Powell failed to clear David Wright's low cross and Walters forced the ball home from close range.