Five people, including three children, were taken to Glan Clwyd Hospital after suffering smoke inhalation.
The fire, at the home in Ffynnongroew Road, started at about 09:15 BST after one of the children switched on the cooker, which had pans left on it.
The family left the house when the smoke alarm went off.
The kitchen was badly damaged by smoke from the blaze which was extinguished before fire crews arrived.
The family was taken to the Bodelwyddan hospital as a precaution.
Jane Honey, deputy head of community safety for the fire service, said: "This highlights the importance of having a working smoke alarm and not to leave combustible items on the hob."
A family was taken to hospital after a child turned on a cooker setting a pan of oil on fire at a house in Rhyl, North Wales fire service has said.