The Bach Long suspension bridge, which translates as "White Dragon", is in Son La province, northwest of the capital, Hanoi, and bordering Laos.
"I dared not look down as I am afraid of heights," said one visitor, Vi Thi Thu, 22, who ventured onto the bridge after attending Saturday's opening ceremony, which included dragon dancing and ribbon cutting.
The reinforced glass used for the bridge has three layers, each 40mm thick, and can hold up to 450 people at a time, according to a statement from the facility's owner.
The bridge is 290 metres long between two peaks on either side of a gorge, plus a 342-metre pathway on the cliffside.
Guinness World Records lists a 562-metre glass-bottomed bridge in Qingyuan, in China's Guangdong province, as the world's longest.
"The engineering required to build that into the side of a cliff but maintain all the features of nature, the greenery, the rocks, it's been an amazing project," said Glen Pollard, a representative of Guinness World Record, who attended the opening ceremony.
The World Record Association, also a record-certifying body, has listed the two-part Vietnamese bridge as the world's longest at 632 metres. Another visitor at the opening ceremony said he quickly overcame initial nerves when walking on the bridge.
"At first it makes you panic, but then if you walked over around 10 glass panels, that feeling is gone," said Tran Xuan Tinh, 72.
