The star later apologized. "I apologize to Valerie Jarrett and to all Americans. I am truly sorry for making a bad joke about her politics and her looks. I should have known better. Forgive me-my joke was in bad taste," Barr said.
But the damage was done. ABC announced within hours that it would end the program.
"Roseanne's Twitter statement is abhorrent, repugnant and inconsistent with our values, and we have decided to cancel her show," Channing Dungey, president of ABC Entertainment, said in a statement Tuesday.
Barr's talent agency, ICM Partners, also wrote in an internal memo that it had dropped her as a client, according to The Hollywood Reporter.
Though she may be the most famous example to date, Barr isn't the first person to lose their job over a social media post.
In 2017, CBS executive Hayley Geftman-Gold was fired for a Facebook comment in which she said that she did not have sympathy for the victims of the mass shooting at a concert in Las Vegas because "country music fans are often Republican gun-toters." She later released an apology.