During a session at the Sydney Writers' Festival, he was confronted by Zinzi Clemmons, who alleged he had forcibly kissed her six years ago.
Two other female writers have since accused him of misogynistic remarks.
Speaking to the New York Times, Mr Diaz, 49, said he took responsibility for his past.
Last month the Dominican-American author - who won the Pulitzer for his book The Brief Wondrous Life of Oscar Wao - wrote an article describing how he was raped as a child.
During an event at the Sydney Writers' Festival, Ms Clemmons referred to the article and then asked him why he had treated her the way he had, attendees told the New York Times newspaper.
She then repeated the allegation on social media, saying the incident took place when she was aged 26 and alleging that she was "far from the only one" he had sexually harassed.
As a grad student, I invited Junot Diaz to speak to a workshop on issues of representation in literature. I was an unknown wide-eyed 26 yo, and he used it as an opportunity to corner and forcibly kiss me. I'm far from the only one he's done this 2, I refuse to be silent anymore.
She added that she believed that Mr Diaz's article about his experience of rape had been written to distract attention from allegations about his behaviour that he feared were about to emerge.
In Mr Diaz's piece in the New Yorker, he said that after being raped he suffered depression and "uncontrollable rage". He said his later relationships with women were troubled and he found it hard to remain faithful.
In his statement, Mr Diaz did not address Ms Clemmons's allegation directly but said it was vital to teach men about consent.
"I take responsibility for my past. That is the reason I made the decision to tell the truth of my rape and its damaging aftermath. This conversation is important and must continue," he said.
"I am listening to and learning from women's stories in this essential and overdue cultural movement. We must continue to teach all men about consent and boundaries."
Two more female US authors have since said that Mr Diaz behaved aggressively towards them.
Carmen Maria Machado said he "slid into bullying and misogyny" after she criticised one of his character's relationships with women.
Monica Byrne said Mr Diaz shouted "rape" in her face after she disagreed with him about something. It was "completely bizarre, disproportionate, and violent", she said, adding that she had "never experienced such virulent misogyny".
There have been a series of harassment allegations made against authors in recent months.
On Friday the organisation that decides the Nobel Prize for Literature said it would not announce an award this year after it was engulfed in a scandal over its handling of allegations against the husband of a member.
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