The 32-year-old, voted Player of the Year at Pride Park for the 2016-17 campaign, also has the option of a further 12-month extension.
Carson has again been a key figure for Derby this term, starting all 27 of the Championship promotion chasers' league games, and he is happy to continue playing a big part going forward.
"It was an easy decision. As soon as I was asked the question I was delighted to commit my future," he told the club's official website. "I've said it a million times since I've been at Derby County - I love it here.
"I am settled and I want to keep things going as they have been. I had to work as hard as I have ever done to get the number one spot; I had to compete with Lee Grant at first who had been the first choice for a few seasons.
"Thankfully I got the opportunity and I've never looked back from that point."
Carson has kept 13 clean sheets this term for a Derby side boasting the second-best defensive record in the division, behind only Wolverhampton Wanderers.