In a statement Barr acknowledged as her own, she said: "I deeply regret my comments from late last night on Twitter. Above all, I want to apologize to Valerie Jarrett, as well as to ABC and the cast and crew of the Roseanne show. I am sorry for making a thoughtless joke that does not reflect my values - I love all people and am very sorry. Today my words caused hundreds of hardworking people to lose their jobs. I also sincerely apologize to the audience that has embraced my work for decades. I apologize from the bottom of my heart and hope you can find it in your hearts to forgive me."
The comedian then retweeted messages from supporters who defend the tweet that got her show canceled.
Barr tweeted: "hey guys, don't defend me, it's sweet of you 2 try, but...losing my show is 0 compared 2 being labelled a racist over one tweet-that I regret even more."
Barr tweet: guys I did something unforgiveable so do not defend me. It was 2 in the morning and I was ambien tweeting-it was memorial day too-i went 2 far & do not want it defended-it was egregious Indefensible. I made a mistake I wish I hadn't but...don't defend it please. ty
But that sentiment contrasted with many retweets from the comedian. Her Twitter timeline shows that, before and after asking fans not to defend her, she retweeted messages suggesting Barr's critics are hypocritical or otherwise defending her original, racist remarks.
Barr also retweeted a post from a user who said her "apology is not sincere."
ABC on Tuesday announced the cancellation of the hit sitcom "Roseanne" following "abhorrent" comments from the show's star. Just an hour later, Barr's talent agency ICM Partners dropped her as a client, the firm confirmed to CNBC.
Barr's abrupt downfall comes after a year of successes, including record ratings for her show's debut and a congratulatory call from the president. Throughout, however, Barr has attracted criticism for her use of social media to provoke, attack, and spread conspiracy theories.
According to consulting firm Kantar Media, "Roseanne" generated revenue of $45 million between March and May of this year.
"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.
After controversy erupted about her tweet, Barr posted this message: "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."
—CNBC's Craig Dale, Tucker Higgins, and Kevin Breuninger contributed to this report.