Twenty-one universities in Canada announced on Thursday the hiring of dozens of researchers to join their top academic ranks, poaching the majority of the recruits from the United States.

Of the incoming 64 researchers, 48 will leave American campuses including Harvard, Yale and M.I.T., and the remainder are from Europe, Asia and Australia.

Turmoil in American academia, precipitated by a crackdown on prestigious universities by the Trump administration and attacks on scientific research groups, has allowed Canada a rare opportunity to lure some of those schools’ top minds north.

Their hiring is paid for through a Canadian government investment of more than 500 million Canadian dollars (about $364 million) in research fields that are strategically important, from global warming to artificial intelligence. The program was announced last December as part of a broader $1.2 billion investment in Canadian innovation projects, with a second round of 63 academics to be hired next year.

While scientists often shy away from political discourse, some are saying the Trump administration’s assault on science is behind their departure.

“I used to live in the country that I thought was the most enthusiastic about the prospects for science improving the human condition, of any country in the world,” said Phillip Zamore, the chair of RNA Therapeutics Institute at the University of Massachusetts. “And I woke up one day and that wasn’t true anymore.”

He has been recruited to McGill University in Montreal, which has also hired five other researchers, and will join the medical faculty.

“If scientists don’t stand up for truth, no one will,” Dr. Zamore said.

The Canada-bound brain drain from U.S. institutions began last year as the Trump administration put forward policies that targeted foreign students, academic freedom and funding for equity-related programs.

Kevin Hall, a nutrition scientist who left the U.S. National Institutes of Health last year, accusing federal officials of censoring his research on ultraprocessed foods, has been hired at the University of Ottawa.

“While certain countries are cutting research and turning their back on academic freedom, we’re doubling down on science,” Mélanie Joly, Canada’s industry minister, told reporters at the announcement, in Vancouver, of the new university hiring. She billed it as the world’s “largest talent attraction” project. The European Union has made a similar push.

“Years from now, we will look back at today’s announcement, and we will be able to seize the lasting impact of our choices,” Ms. Joly said.

Unpredictable decisions about funding prompted Seth Guikema, a professor in civil and environmental engineering, who has specialized in natural hazards modeling at the University of Michigan, to look elsewhere. His work focuses on how climate hazards inequitably affect communities, and that work has become harder to fund, he said.

“Every country sets its priorities in terms of what is going to get funded, and I think Canada has done a very good job of supporting research in areas that really matter to society,” said Dr. Guikema, who will start at Western University in London, Ontario in January.

The University of Toronto has also recruited six academics, including Sara Seager, a Canadian astrophysicist from the Massachusetts Institute of Technology.

Universities in Canada are the latest pathway for some Americans to leave the United States, citing the Trump administration’s policies. Canada has also expanded citizenship eligibility for people who can prove their Canadian ancestry, resulting in thousands of applications from Americans.