Trachtenberg, also known for her roles in Buffy the Vampire Slayer and Harriet the Spy, was found dead in her New York City apartment just after 8am local time on Wednesday (26 February).
Her death is not being treated as suspicious and the police said the medical examiner will determine the cause of her death.
Blake Lively has issued an emotional tribute to her former Gossip Girl co-star Michelle Trachtenberg (Warner Bros.)
“It is with great sadness to confirm that Michelle has passed away,” the actor’s representative said.
“The family requests privacy for their loss. There are no further details at this time.”
Taking to Instagram, Lively captioned a photo of the pair, which read: “Everything she did, she did 200 percent.
“She laughed the fullest at someone’s joke, she faced authority head on when she felt something was wrong, she cared deeply about her work, she was proud to be a part of this community and industry as painful as it could be sometimes, she was fiercely loyal to her friends and brave for those she loved, she was big and bold and distinctly herself.
Lively praised Trachtenberg’s work ethic (Warner Bros.)
“Time passes. You take for granted that you get the chance to see an old friend.
“To paraphrase, the real tragedies in life are the ones that blindside you on an idle Tuesday.
“Hold those you love and have loved dear.”
The 37-year-old, who starred as Serena van der Woodsen from 2008 to 2012, added: “The world lost a deeply sensitive and good person in Michelle.
“May her work and her huge heart be remembered by those who were lucky enough to experience her fire.”
Trachtenberg played young socialite Georgina Sparks of Manhattan’s Upper East Side who created havoc throughout the show.
Fellow Gossip Girl star Ed Westwick shared a tribute yesterday (26 February) on social media, which read: “So sad to hear of the passing of @michelletrachtenberg sending prayers.”
Buffy the Vampire Slayer star Trachtenberg passed away at the age of 39 (UPN)
Her Buffy the Vampire Slayer co-stars also said goodbye to their ‘little sister’.
Trachtenberg was best known for playing Dawn Summers, the younger sister of character Buffy, starring Sarah Michelle Gellar.
Emma Caulfield, who starred as Anya Jenkins in the series, took to her Instagram Story where she referred to Trachtenberg as ‘Mish Mish’.
Caulfield wrote: “I’m so sorry your bright light died so young. Our Buffy family lost a little sister today.
“Rest in peace lovely Mish Mish. You were loved.”
Alyson Hannigan, who played Willow Rosenberg, added: “I am deeply saddened by the news of Michelle’s passing.
“She brought a loving energy to the set of Buffy. My thoughts are with Michelle’s family and friends.”
Another co-star, David Boreanaz, said: “So very sad. Horrible news.”
