Donald Trump Jr told Fox News the meeting was "just a nothing" but he should have handled it differently.
He released emails showing he welcomed an offer to meet the lawyer, who was allegedly linked to the Kremlin and had material damaging to Hillary Clinton.
US officials are investigating alleged Russian meddling in the US election.
Since he was elected, President Trump has been dogged by allegations that Russia tried to sabotage Mrs Clinton's campaign.
He has denied any knowledge of this and Russia has also repeatedly denied interfering.
Asked by Fox News' Sean Hannity if he had told his father about last year's meeting, Mr Trump Jr said: "No. It was just a nothing. There was nothing to tell.
"I mean, I wouldn't have even remembered it until you started scouring through this stuff. It was literally just a wasted 20 minutes, which was a shame."
Donald Trump Jr, his brother-in-law Jared Kushner and campaign chairman Paul Manafort met Russian lawyer Natalia Veselnitskaya at Trump Tower in New York in June 2016.