That tweet capped off a series of others attacking congressional Republicans who apparently, for her, gave unsatisfactory answers to questions about Trump's comments.
"Stop selling the country out for this corrupt president. It would serve you well to buck up and be a patriot just this once," she also said.
Her comments came just after ABC released footage of Trump saying he would listen to some foreign opposition research without necessarily telling the FBI.
Brzezinski specifically called out House Minority Leader Kevin McCarthy, R-Calif., as well as two Republican senators.
"How do these cowards look in the mirror. Don’t you know THIS ENDS BADLY. #Disgraceful," she tweeted alongside a report about McCarthy ignoring Trump's comments.
Trump responded to the controversy by tweeting on Thursday that it was "ridiculous" to expect him to call the FBI.
He also accused House Intelligence Committee Chairman Adam Schiff, D-Calif., and Senate Intelligence Committee Vice Chairman Mark Warner, D-Va., of refusing to call the FBI after speaking with apparent Russian operatives.