In the program, "City without Electric Light", Hoi An will switch off its lights for an hour between 8.30pm to 9.30pm this weekend.
All old streets will light up with candies and oil lamps during that hour.
As scheduled, local people will join to clean rubbish on Cua Dai Beach and in the old quarter in the morning, while the Earth Hour's goodwill ambassadors will canvass the streets calling for environmental protection.
An art performance will be held at Hoai River Square, while over 3,000 floating lanterns will be released on the river.
It's the fourth time the city has organized the Earth Hour, launched by the World Wildlife Fund.
The city also launched its free wireless internet network on March 28.
It means that tourists can access internet anywhere within the old quarter.