The woman, whose identity has not been revealed, had flown with her family on Vietnam Airlines flight VN1379 from Hue in central Vietnam to the Tan Son Nhat airport in HCMC on Monday.
When she was getting off the plane on its stairs, she fell, hit her head and bled from a head injury.
She was taken to the Military Hospital 175 soon after, but died on Tuesday, according to a press release from the national flag carrier.
At the time of the incident, the ramp was dry. It was not raining that day.
The national carrier said the incident was "deeply regrettable," adding that it was cooperating with authorities to figure out the cause of the accident and undertake procedures to ensure the rights of passengers.