Hertfordshire Fire Service received a call to the address in Cadmore Lane, Cheshunt, at 5.51am on Saturday.
Firefighters battled to tackle the blaze, which was “well-established” on the first floor and roof of the building, Hertfordshire County Council said.
Three people were taken to hospital with minor burns and smoke inhalation, East of England Ambulance Service said.
Hertfordshire County Council said in a statement: “Hertfordshire Fire and Rescue were called at 5.51am to a fire at a residential care home in Cadmore Lane, Cheshunt.
“Firefighters were faced with an extremely fierce fire, well-established in the first floor and the roof of the building, which has since collapsed.
“Thirty-three residents were rescued and firefighters worked closely with police and ambulance colleagues to evacuate them to a nearby emergency reception centre.
“Sadly, we can confirm that two people died in the fire and we would like to offer our sympathies to their families.”
A spokesman for East of England Ambulance Service said: “Five ambulance crews, two ambulance officers, Hazardous Area Response Team (Hart) and volunteer doctor were dispatched.
“They worked closely with fire service and police colleagues to evacuate residents and assess them at a nearby rest centre.
“Thirty-three people were assessed at the scene and three patients with minor burns and smoke inhalation were taken to Princess Alexandra Hospital for further care.”
Hertfordshire Police said officers had assisted with the evacuation of the building and helped to transport residents to an emergency reception centre.
A spokeswoman said investigations were being led by the fire service at this stage.
More than £600 has already been raised through an online fund set up to help residents of the care home in the aftermath of the blaze.
Hertfordshire County Council said it was working with Broxbourne Council and the health service to assess the needs of evacuated residents and arrange alternative accommodation.