The Mid-Autumn festival is named "Têt Trung Thu" in Vietnamese.
It’s a custom for the Vietnamese to carry carp-shaped lanterns and play outside during the night of the Mid-Autumn Festival. Lantern fairs and lion-waving performances are held in various places, such as Ho Chi Minh City and Hanoi.
The meaning of Mid-Autumn Day is rather different to that in China, though the Vietnamese also celebrate it and eat mooncakes. In Vietnam the Mid-Autumn Festival is the happiest day for children, during which parents buy their children various kinds of lanterns and snacks.
As for origin of the Mid-Autumn Festival in Vietnam, it’s totally different from the Chinese version (Chang E Flying to the Moon). Rice is harvested before the 15th of the eighth lunar month in Vietnam. Each household then offers sacrifices to the God of Earth. While occupied with harvesting parents have not so much time to take care of their children, therefore they make full use of the festival holiday to play with their children.
Parents tell stories about A Gui (a legendary figure in Vietnamese mythology) during the Mid-Autumn Festival. According to legend, there was an evil carp (spirit), which took on human form, and killed many people at night. A Gui figured out a way to kill it by putting up carp lanterns throughout the village, and as a result Vietnamese children carry carp lanterns on the streets during the festival to exorcise evil spirits.
Lantern fairs are held throughout Vietnam during Mid-Autumn Festival, during which lion-waving performances are held by the locals. Family members unite around a table in their yards and eat mooncakes and snacks while appreciating the moon. Children chase one another, carrying lanterns of various shapes, on the streets.