A group of five, which included family members, arrived in the capital two days after a blast hit a tour bus killing three Vietnamese holidaymakers and an Egyptian guide.
It was not immediately clear if representatives of the tour company that arranged the trip were part of the group.
The attack, which took place in the Giza governorate, wounded 11 other Vietnamese tourists and an Egyptian bus driver, Egypt's public prosecutor said.
There was no immediate claim of responsibility for the attack.
The group was received at Cairo International Airport on Sunday by the deputy Vietnamese ambassador to Egypt and representatives from Egypt's tourism, health and foreign ministries, the source said.
Saigon Tourist, the company that organised the trip, had said the Vietnamese tourists were "on their way to a restaurant for dinner" when the bomb exploded.
Company officials were heading to Cairo on Saturday and plans were made to allow some relatives of the victims to also fly to Egypt.
One of those heading to Egypt was Nguyen Nguyen Vu whose sister Nguyen Thuy Quynh, 56, died in the bombing, while her husband, Le Duc Minh, was wounded.
The couple, both aged 56, were in the seafood business and holidaying in Egypt when the tragedy occurred, Quynh's younger brother said.
"We were all very shocked... My sister and her husband travel quite a lot and they are quite experienced in travelling abroad. Their hobby is travelling," Vu told AFP.
Egypt's tourism industry has been struggling to recover from terror attacks and domestic instability that followed the 2011 uprising that toppled longtime ruler Hosni Mubarak.
Visitors to Egypt reached 8.2 million people in 2017, up from 5.3 million the year before.
The figures remain a far cry from the 14.7 million who visited Egypt in the year before the uprising.