Many took selfies with the dinosaur, named "Shen", the Chinese word for god, which measures 12.2 meters long and 4.6 meters high and weighs 1,400 kg.
The T-Rex, which would have lived 66-68 million years ago, was unearthed in Montana, in the United States, in 2020.
"We knew the grandchildren are so into dinosaurs. They're always like 'dinosaur this, dinosaur that', so we thought, 'wow, it's such a good experience to bring them to have a look at this real thing'," retiree Nancy Seet said.
Dinosaur enthusiast Richard Chan, 37, said he was reliving his childhood.
"I collect a lot of Jurassic Park T-Rex figurines so really cool to see an actual one," said Chan. When Shen is sold, it will be the first auction of a T-Rex fossil in Asia, according to Christie's.
Some experts have expressed concern that such significant items should not be auctioned to private collectors, where they may not be available to the public or to scientists.
Francis Belin, president at Christie’s Asia Pacific, said they hoped that exceptional objects ended up in institutions so they could be seen by the public.
A guide price was not provided for Shen, nor the identity of the seller, but Belin said a previous T-Rex skeleton "Stan" fetched $31.8 million at a sale in New York in 2020. Shen the T-Rex is on public view for three days until Sunday.
The auction in Hong Kong takes place on Nov. 30.