Speaking to reporters later, Trump said George Conway is a "wack job," adding: "Kellyanne is a wonderful woman. He's doing a tremendous disservice to a wife and family."
George Conway responded less than 20 minutes after Trump's morning tweet.
"You seem determined to prove my point. Good for you!" he tweeted, adding: "#NarcissisticPersonalityDisorder."
In a subsequent tweet directed at Trump, he added: "You. Are. Nuts."
Kellyanne Conway defended Trump during an interview with Politico, calling him a "counterpuncher".
"You think he shouldn't respond when somebody, a nonmedical professional accuses him of having a mental disorder?" Conway said, according to the publication. "You think he should just take that sitting down?"
She did not immediately return a call from the Washington Post seeking comment.
George Conway has pushed back on several of Trump's assertions, including the notion that Trump decided not to give him a job.
Conway said that he opted against working in the Justice Department after Trump offered him a position heading the civil division because he watched Trump attack the department's leaders and then fire James Comey as FBI Director in May 2017.
Conway shared a letter he wrote to Trump, dated May 31, 2017, in which he thanked Trump for selecting him for the job but said he was backing out.
"I have reluctantly concluded, however, that for me and my family, this is not the right time for me to leave the private sector and take on a new role in the federal government," Conway wrote. "Kellyanne and I continue to support you and your Administration, and I look forward to doing so in whatever way I can from outside government."
It was unclear what Trump meant by his assertion in his tweet that Kellyanne Conway had a role in denying her husband a job.
Conway said that he has had a number of notable interactions with Trump over the past decade, often concerning legal representation and sensitive legal matters since Trump became president.
Today was the second consecutive day that Trump has used Twitter to attack George Conway. In a much shorter tweet yesterday, he called him a "loser."
George Conway has been a persistent critic of Trump's policies and actions, frequently going on Twitter to question whether the President is operating within the Constitution and other accepted boundaries. But the criticism recently has become more personal, and he has often attacked Trump just after his wife has defended the President on television.
In tweets on Tuesday, Conway included images from the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders, including pages with diagnostic criteria for "narcissistic personality disorder" and "antisocial personality disorder."
Yesterday, Conway said his tweets questioning the President's mental health were aimed in part at avoiding conflicts with his wife.
"It's so maddening to watch," Conway said. "The mendacity, the incompetence, it's just maddening to watch. The tweeting is just the way to get it out of the way, so I can get it off my chest and move on with my life that day. That's basically it. Frankly, it's so I don't end up screaming at her about it."
