Is one hour enough time?

Where are you changing planes to? In Schengen or out of Schengen?

If going to a non-Schengen country, you stay in the general area of your arrival and head off to your next gate.

If to a Schengen country, you will have to clear Passport Contol at Keflavik.

Either way, Keflavik is very efficient at doing this. Unless your arriving plane is very late, you should be okay.

Thank you, I will be arriving at Keflavik from Amsterdam change planes (still with Iceland Air) and continue on to Seattle.

We flew IcelandAir out of Seattle last summer and had a short layover in Reykjavik (55-60) minutes before flying to Munich.
Initially, I was worried about the short layover, but my daughter had flown IcelandAir the previous summer and convinced me it would be fine---and she was right, it was plenty of time. The airport is small enough to get to your next flight smoothly.

Yeah, one hour at Keflavík is usually fine. The airport’s pretty small and easy to get around, and Icelandair sets up their connections so you can make them. You don’t have to re‑check bags, but you might have to go through passport control depending on where you’re flying to or from, which can slow things down a bit. As long as your first flight isn’t late, you should be okay, just head straight to your gate and don’t linger. If something does go wrong, Icelandair will rebook you since it’s their connection

.FYI...you will have to go through exit passport control at Keflavik as that is where you are leaving the Schengen zone.

Hah! Just googled and realized for the first time that Iceland is a member of the Schengen area even though it's not a member of EU. Thanks Frank II !!