He also referred to her "bleeding badly from a facelift" and assailed her co-presenter Joe Scarborough.
Senator Lindsey Graham said Mr Trump's remarks were "beneath the office" of president.
He said the tweet "represents what is wrong with American politics, not the greatness of America".
"Please just stop. This isn't normal," tweeted fellow Republican Senator Ben Sasse.
Republican House Speaker Paul Ryan also joined the criticism, saying: "I don't see that as an appropriate comment. What we're trying to do around here is improve the tone, the civility of the debate. This obviously doesn't help."
MSNBC said it was "a sad day for America when the president spends his time bullying, lying and spewing petty personal attacks instead of doing his job".
But the White House sprang to Mr Trump's defence.
"I don't think that the president has ever been someone that gets attacked and doesn't push back," spokeswoman Sarah Huckabee Sanders told Fox News.
"People on that [MSNBC] show have personally attacked him many times. This is a president who fights fire with fire and certainly will not be allowed to be bullied by liberal media and the liberal elites within the media, or Hollywood or anywhere else."
Brzezinski and Scarborough co-present the MSNBC breakfast show, Morning Joe, which has increasingly derided President Trump since he took office.
In recent weeks, Scarborough has called him a "bumbling dope", resembling "a kid who pooped in his pants", while Brzezinski has mocked members of the administration as "lobotomised".
"I heard poorly rated @Morning_Joe speaks badly of me (don't watch anymore)," Mr Trump tweeted on Thursday morning.
He accused "low I.Q. Crazy Mika" and "Psycho Joe" of "insisting on joining me" at his Mar-a-Lago Florida golf resort over three days at New Year's Eve.
"She was bleeding badly from a face-lift. I said no!" he added.
The senior Democrat in the House of Representatives, Nancy Pelosi, called Mr Trump's tweets "sexist, an assault on the freedom of the press & an insult to all women".
Brzezinski is the daughter of the late Zbigniew Brzezinski, who was an aide to presidents Carter and Johnson, while Scarborough is a former Republican congressman. The couple are engaged to each other.
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