Shore's son, actor Pauly Shore, said on Twitter that his mother passed away early Wednesday morning at 87 years old.
"My heart lays heavy," he said in the tweet.
The Comedy Store also tweeted Wednesday about Mitzi Shore's passing, describing her as "an extraordinary woman and leader who identified, cultivated and celebrated comedy's best performers."
"She helped change the face of comedy and leaves behind an indelible mark and legacy in the entertainment industry and stand-up community. We will all miss her dearly," the establishment said in a second tweet, adding that its doors will be closed on Wednesday.
Richard Pryor, Jim Carrey, David Letterman, Roseanne Barr and Robin Williams, and many other comedic talents, all started their careers at the Comedy Store.