Mai Duong, 34, had made a desperate online plea and a global search was undertaken to find either a bone marrow or cord blood stem for a transplant.
Duong said the umbilical cord came from a woman who decided to donate it, instead of tossing it in the garbage.
"There is a mother somewhere in the world who gave birth and who has given another mother a second chance," she told a news conference.
"I'm very, very grateful for that lady who we're never going to meet."
Duong said she will now have to spend the next six to eight weeks in hospital in isolation away from her four-year-old daughter.
"It's going to be to have more treatments, chemotherapy, radiation therapy and then I'm going to have the transplant and hopefully everything will go well," she said.
"I just hope that I'm going to beat cancer once and for all."
Duong faces a long uncertain road ahead even though doctors now have cord blood.
"It's a big milestone, for sure," she said. "But things can go wrong again down the road like it went for me the first time, so I'm not going to celebrate it until I'm completely out of the woods."
Duong successfully fought off acute leukemia in 2013 with chemotherapy. She had to terminate a 15-week pregnancy to undergo the treatment.
Duong was in remission until a blood test revealed leukemia had returned this past May.
The use of an umbilical cord is a medical advance that has only been available for the past five years.
The option of using stem cells from a brother or sister is only possible in one out of four cases and Duong's brother was not compatible.
Hematologist Lambert Busque told reporters that finding a perfectly compatible donor is even more difficult — especially for those who are from a non-Caucasian background.
"The statistics for certain patients are like winning the lottery," he said.
There's a serious lack of minorities on stem cell donor lists.
Internationally, only about one per cent of the 24 million listed donors are of Asian background.
Canada Blood Services, which manages the stem cell and marrow registry outside Quebec, said in August that 340,837 people were registered in the rest of the country. Of them, 71 per cent were Caucasian, with the rest qualifying as "ethnically diverse'' or of unknown origin.
Hema-Quebec, the organization that manages the province's list, said at the time that about three per cent of the 47,000 stem-cell donors were of Asian descent and only a fraction of those were Vietnamese. The ratios are similar among international donors and Vietnam doesn't have a registry of its own.