A hospital doctor in the city of Babahoyo declared Bella Montoya, 76, dead following a suspected stroke.
She was placed in a coffin and taken to a funeral parlour, where relatives held a vigil before her planned burial.
When, after almost five hours, they opened the coffin to change her clothes ahead of the funeral, the woman gasped for air.
“My mum started to move her left hand, to open her eyes, her mouth; she struggled to breathe,” her son Gilbert Balberán described the moment he realised his mother was still alive.
Video taken by one of the mourners shows her lying in an open casket struggling to breathe, while another complains that an ambulance they called has not yet arrived.
Minutes later, firefighters arrive and lift Bella Montoya from the coffin onto a stretcher and take her back to the same hospital where she had been declared dead.
Her son told Ecuadorean media that she was in intensive care, but was responsive.
“My mum is on oxygen, her heart is stable. The doctor pinched her hand and she reacted, they tell me that’s good because it means she is reacting little by little,” newspaper El Universo quoted him as saying.
Ecuador’s health ministry has set up a committee to investigate the incident.
Mr Balberán said he had taken his mother to hospital at about 09:00 “and at noon a doctor told me [she] died”.
He said he had even been issued with a death certificate, which stated that she had died of cardiopulmonary arrest after suffering a stroke.
Bella Montoya is not the only person to “come alive” after being officially declared dead.
In February, an 82-year-old woman was found to be breathing while lying in a funeral home in New York state. She had been pronounced dead three hours earlier at a nursing home.
