Mr Conway, a lawyer and co-founder of the Lincoln Project, took to Twitter to attack the outgoing president for spreading “destructive lies” about his election loss to Joe Biden.
Mr Trump has refused to concede the election to Mr Biden and continues to make false claims of ballot fraud without providing any credible evidence.
Meanwhile more than 285,000 Americans have been killed during the pandemic and more than 14.75 million people have tested positive.
“A record 3,157 Americans died yesterday from Covid-19, meaning that more than 1 out of 100 of our pandemic fatalities occurred in those 24 hours,” tweeted Mr Conway.
“Meanwhile, a deranged @realDonaldTrump soothes his wounded ego by spreading insane, destructive lies about the election he lost.”
The attorney has been a vocal critic of Mr Trump while his wife worked for him as an advisor and counselor before quitting her position.
Ms Conway, who was also Mr Trump’s 2016 campaign manager, acknowledged that Joe Biden had beaten her former boss for the White House in an interview given on Friday.
“If you look at the vote totals in the Electoral College tally, it looks like Joe Biden and Kamala Harris will prevail,” Ms Conway told The 19th.
“I assume the electors will certify that and it will be official. We, as a nation, will move forward, because we always do.”