"Since you've now called me a liar, I will now call you a silencer. I see your gaslight and now will raise you a scorched earth," Tamblyn said in the letter, published on Wednesday by Teen Vogue
Tamblyn first made the accusation on Monday, after actor Armie Hammer defended his upcoming film, "Call Me By Your Name," against Woods' criticism of the age gap between the movie's two main male characters.
The critically-hailed, coming-of-age movie, which debuted at Sundance, follows a 17-year-old's (Timothée Chalamet) romantic relationship with a 24-year-old academic (Hammer).
Hammer replied, "Didn't you date a 19 year old when you were 60.......?"
Tamblyn chimed in with the story of an alleged encounter with Woods.
"James Woods tried to pick me and my friend up at a restaurant once. He wanted to take us to Vegas," she wrote in a Tweet.
When then 16-year-old Tamblyn told Woods her age, she said he replied, "even better."
Woods claimed the story is a "lie."
Tamblyn recounted her story in more detail in her open letter.
"I told you my age because I thought you would be immediately horrified and take back your offer," she wrote. "You laughed and said, 'Even better. We'll have so much fun, I promise.'"
A representative for Woods has not returned CNN's multiple request for comment.
"The saddest part of this story doesn't even concern me but concerns the universal woman's story. The nation's harmful narrative of disbelieving women first, above all else," Tamblyn wrote. "Asking them to first corroborate or first give proof or first make sure we're not misremembering or first consider the consequences of speaking out or first let men give their side or first just let your sanity come last."
Tamblyn calls on Woods to "go inward now and ask yourself the hard stuff."
"Only you and your darkness know who you are," she wrote. "Only you and your actions know what you've done. That means you and only you have the power to change your behavior."
Tamblyn has been praised on social media for writing the letter.
"What's powerful about @ambertamblyn's action is she no longer accepts the blame. In that way, she frees us all," Lena Dunham wrote.
"True Blood" star Anna Paquin said she loved Tamblyn's "obviously fierce intellect and precise insight into such a troubling aspect of the female experience."