“That’s so disgusting,” she said in an interview with The Young Turks, a progressive online news network.
The DNC emails showed that former DNC chair, Debbie Wasserman Schultz, called Mr Sanders' campaign manager a "damn liar", and that staffers were planning to "smear" him as an atheist.
Ms Schultz has since been called a "friend" of Hillary Clinton and will likely join her campaign.
"What does this really say about us if all of this goes by unattended?" Ms Sarandon asked.
Democratic National Convention 2016 in pictures
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Some people were surprised to see the 69-year-old actress, who frequently appeared as a surrogate for Mr Sanders, appear at the convention in Philadelphia on Monday evening.
Social media users pointed out that she did not look pleased with the convention result.
Others went as far as to suggest she was having a terrible time - “literally the worst time.”
Sarandon was quick to respond.
“Accurate,” she tweeted.
Ms Sarandon has been a strong critic of Hillary Clinton, claiming it would be "inevitable" that Ms Clinton would be indicted for the misuse of her personal email server.
In the end, Ms Clinton was not prosecuted.
The actress also said that Ms Clinton would be "more dangerous" as president than Republican Donald Trump.
Mr Sanders gave a rousing speech at the convention. Despite his "disappointment" to hear of the DNC scandal, he still urged attendees and delegates to vote for his former rival.
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