The family of Alba Maruri were informed of her death last month and later sent what they were told were her ashes.
But Ms Maruri awoke from a three-week coma in hospital on Thursday and asked doctors to call her sister.
Her family were overjoyed at the news - but are unclear whose ashes they have in their home.
The hospital has apologised for the mix-up. Ms Maruri lives in the city of Guayaquil, the epicentre of Ecuador's Covid-19 outbreak.
Ecuador has been badly affected by the pandemic, with more than 22,000 cases and nearly 600 reported deaths.
According to local newspaper El Comercio, Ms Maruri was admitted to hospital last month with a high fever and breathing difficulties.
On 27 March her family were told she had died. They were shown a corpse in the hospital morgue, but had to be kept at a distance because of the fear of contagion.
Ms Maruri's nephew, Jaime Morla, told hospital officials he thought it was his aunt.
"I was afraid to see her face," he told AFP. "I was a metre and a half away. She had the same hair, the same skin tone."
The body was taken away and cremated, and the ashes sent to the family.
But then on Thursday, Ms Maruri regained consciousness and told the astonished doctors her name. She provided them with her home phone number and asked for her sister, Aura, to pick her up.
A team from the hospital visited the family home to apologise, El Comercio reported, and said the hospital had been in chaos at the time because of the number of coronavirus cases and deaths.
"It is a miracle. For nearly a month we thought she was dead. Imagine," said Aura. "And I have someone else's ashes."
The family say they want authorities to compensate them for the mix-up and to reimburse the cost of the cremation.
Ms Maruri has also been bought a new mattress as her family had thrown her old one away.