When researching this claim I found a few things. Zohran Mamdani did tell a story about how his aunt was afraid to wear a hijab on the subway post 9/11 due to Islamaphobia all across the country, but especially in NYC after the 9/11 terrorist attacks. This statement did face backlash. Many republican nationals, including vice president JD Vance mocked Mamdani's story. Mostly due to the fact that it wasnt actually Mamdani's "aunt". It was his fathers cousin. Mamdani is facing scrutiny for lying about the story, even though it was a relatively minor lie. Many republicans are even going as far to say that Mamdani cant be trusted because he is seen "lying" on this occasion. Mamdanis initial reasoning behind telling the story was his concern of Islamophobia and hate in New York City
 
https://www.foxnews.com/video/6384160055112
This is a video of Mamdani clearing up confusion on his statement. In this interview, he is defending his claim and stating he refers to his fathers cousin as his aunt and thats who he was referring to in his initial statement.
https://www.cnn.com/2025/10/24/politics/zohran-mamdani-islam-cuomo
In this video, Mamdani is delivering a speech on the importance of his islamic faith. This speech is where he tells the story of his "aunt" and how she faced Islamophobia after the 9/11 terrorist attacks.
https://www.foxnews.com/politics/mamdani-forced-clarify-relative-invoked-viral-islamophobia-anecdote-questions-swirl
This article mainly talks about how many people poked holes in Mamdanis story and found some irregularities. Many republicans are criticizing Mamdani for lying about the story and embellishing the story.
https://www.cnn.com/2025/10/28/politics/zohran-mamdani-sept-11-aunt
This article talks about how Mamdani is passionate about his Islamic faith, and how some of his family members have had to face Islamophobia in the past.
Fox news is a known right leaning news outlet. This could lead them to speaking about Mamdani more negatively, considering he is the democratic candidate for the NYC Mayor. They also may favor Andrew Cuomo, the Republican candidate for mayor.
CNN is a commonly left leaning news outlet. This could lead them to defending Mamdani more so than Fox would. The language also seemed to be more positive when speaking about Mamdani compared to Fox News.
Both news outlets state how Mamdani is facing backlash for his telling of the story and about how he twisted the truth in a way.
There is not really any evidence that undermines the claim I am fact checking. Only the fact that the main reason Mamdani is being criticized is because he lied about part of the story, not because he told the story.