The lawyer, according to an intermediary, had claimed to have damaging information on Hillary Clinton.
White House spokeswoman Sarah Huckabee Sanders read Trump's statement during a Tuesday briefing with reporters:
"My son is a high quality person and I applaud his transparency," Trump said.
At midday, Trump Jr. released a chain of emails in an effort "to be totally transparent."
Times deputy managing editor Clifford Levy tweeted that Trump Jr. released the emails after he learned the newspaper was writing about them.
At the White House briefing, Sanders declined to comment further on the matter and referred questions to Trump Jr.'s legal representation.
When pressed for the president's reaction to the reports surrounding his son's meeting, Sanders said that the elder Trump is "frustrated with the process and the fact that this continues to be an issue."
The president's son forwarded the final email to his brother-in-law, Jared Kushner. When asked if Kushner still had his security clearance, Sanders said that the White House doesn't publicly discuss the security clearance of its personnel.