Tomei called the news "an incredible gift."
On Tuesday night's episode of PBS' Finding Your Roots, Tomei discovered that she has a famous cousin, Julianne Moore! Henry Louis Gates Jr., the show's host, told Tomei the exciting news and she was thrilled to learn of her familial relation to her longtime friend.
"Julianne? Julianne! Julie? You know we went to school together?" 54-year-old Tomei asked, referencing her and Moore's time at Boston University. "Jules! Oh, I can't wait to tell her."
The show went on to explain that the women, who co-starred in Crazy, Stupid, Love in 2011, share "an identical stretch of DNA along their X chromosome."
"Ironically, Julianne has no Italian ancestors that we know of. And every ancestor we could name on Marisa's tree has roots in Italy," the Finding Your Roots voice over noted. "A powerful demonstration of how DNA can bridge the divide that appears to exist between people of diverse origins."
Tomei, 54, was thrilled with the news, sharing the video and pics of her with Moore, 58, on Instagram.
"What an incredible gift to find out about my family’s roots with @HenryLouisGates!" Tomei wrote. "Eternally grateful for this generation and generations to come.... and the big surprise — discovering my friend is my REAL cousin! Hey cuz @juliannemoore!!!! Love"
Moore was just as excited about her new kin, sharing a snippet from the show on Instagram and exclaiming, "I KNEW WE WERE ALIKE! @marisatomei is my COUSIN!! OMG I’m so excited, thank you @henrylouisgates for letting us know we have identical segments of DNA - #FindingYourRoots #twinning"
Watch the video below for more famous family connections: