"He is such a phony," Reid said today in an interview with CNN after Trump said he believed President Obama was born in the United States but falsely accused Hillary Clinton of spreading the theory in her 2008 presidential campaign.
Reid also predicted Trump would lose the election, and called him an "absolute fraud."
Speaking to reporters on Capitol Hill on Tuesday, the Nevada Democrat called for more scrutiny of the 70-year-old Republican's health.
Asked about Reid's comments in an interview with The Washington Post, Trump mocked Reid's recent injury.
"Harry Reid? I think he should go back and start working out again with his rubber work-out pieces," he said in the interview published Thursday.
Reid broke ribs and bones in his face last year when an exercise band he was using at home snapped, hitting him in the face and sending him to the floor. The Senate's top Democrat is now blind in one eye and has trouble with his balance.
He dismissed Trump's comments in a statement today, calling Trump a "con-artist."
"I may not be able to see out of my right eye, but with my good eye, I can see that Trump is a man who inherited his money and spent his entire life pretending like he earned it," Reid said in the statement.
"In Searchlight, we learned a thing or two about hard work that Trump may not have learned at his boarding school," he added, referring to his hometown in Nevada.
Reid also called Trump a "leech" on the Senate floor this week.
"It's one of the best things I've ever done," Reid said in a new Washington Post interview.