Eduardo Bolsonaro, 35, was elected last year from São Paulo, and serves in the lower House. He is the head of the foreign affairs committee there.

The son’s effusive support of the Trump administration has endeared him to the American president, who singled him out for praise when the father visited the White House in March. The younger Mr. Bolsonaro accompanied the Brazilian leader on that visit and was invited to attend an Oval Office meeting.

During a visit to Washington earlier this year, Eduardo Bolsonaro said undocumented Brazilians living in the United States are “an embarrassment.” During a visit to the White House he wore a baseball cap with the slogan Make America Great Again — Trump 2020.

In February, during a stop at Mar-a-Lago, Mr. Trump’s golf club in Palm Beach, Fla., Eduardo Bolsonaro reminisced about his days working as a federal police officer along Brazil’s border with Bolivia as he hailed the White House’s bid to build a wall along the Mexican border.

“We know how the things work,” he said. “So build that wall! We Brazilians are supporting you!”

Eduardo Bolsonaro told reporters on Thursday that by nominating a son as ambassador to the United States his father would be sending a clear signal of his “strong commitment” to strengthen relations between Brazil and the United States. He added that as ambassador he would strive to rebuild Brazil’s reputation abroad and attract investment.

Unlike several countries in the region, Brazil has built a professional foreign service in which top posts are not used to reward campaign donors and political allies.

The ambassadorship in Washington is seen as the service’s premier overseas post and it has historically been held by officials with distinguished careers in diplomacy and foreign affairs.