"As you said from the beginning, he's winging it," co-host Joe Scarborough told Brzezinski on the program Monday, saying Trump wasn't listening to his top campaign aides.
Brzezinski, who represents the liberal half of duo, said other candidates at the same point in the campaign would be speaking with foreign policy leaders, former politicians and world leaders to more carefully craft their message.
"Instead, he is literally still vomiting out anything he thinks at the tip of his head that he might have seen on TV, and I don't know what channel, recently," she said of Trump.
"It's pathetic, number one. It's sad for the party, it's sad for the country, and it's sad for his candidacy, which could have done so much," she added.
"He could be doing so much better. It is an embarrassment. Every day the embarrassment deepens because he just simply refuses to stop playing to the lowest common denominator," Scarborough said on the show.
The pair focused on Trump's remarks regarding the Orlando nightclub shooting, with Scarborough mentioning Trump's widely reported suggestion that clubgoers should have had weapons to prevent the mass shooting. 
Trump on Monday clarified in a tweet that he "was obviously talking about additional guards or employees" at the Pulse nightclub and not advocating for guests at the club to be armed themselves.
Trump was once a frequent call-in guest to the MSNBC morning show, which was at one time criticized by some for being too chummy with the presumptive GOP nominee. Comedian Larry Wilmore even joked about the subject at this year's White House Correspondents' Association dinner. 
Yet in recent weeks, Brzezinski and Scarborough have hit Trump with scathing criticism, ripping his rhetoric and campaign strategy.