Flaherty died suddenly Thursday at the age of 64. His family said he died peacefully.
In Ottawa, the House of Commons suspended its sitting before question period, after news of Flaherty’s death began to spread.
On Thursday afternoon, Ford tweeted that his prayers go out to Flaherty’s wife, Christine Elliott, and their family.
"The Ford family is heartbroken," the mayor’s tweet said.
Flaherty had served as the MP for Whitby-Oshawa since January of 2006. Until last month, he had been the only finance minister to serve under Prime Minister Stephen Harper.
Before making the leap to federal politics, Flaherty spent 10 years as an MPP in the Ontario legislature. He held several cabinet posts under premiers Mike Harris and Ernie Eves.
Ford's father, Doug Ford Sr., served in the provincial legislature with Flaherty.
When Flaherty announced his resignation from cabinet last month, Ford said that Canada was losing its "best finance minister ever."
That day, Ford also expressed concern about the health problems Flaherty had been battling.
The mayor also said that day that Flaherty had stuck by him "through thick and thin."
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