He volunteered for the unsuccessful campaign of New York City Council primary candidate democratic socialist Khader El-Yateem, a Palestinian Lutheran minister running in Bay Ridge, Brooklyn in 2017.

[14][15][16] In 2019, Mamdani announced his campaign for New York State Assembly in the 36th district, which encompasses Astoria and Long Island City in Queens.

[17] During the campaign, Mamdani was endorsed by the Democratic Socialists of America[18] and ran on statewide rent control, fare-free transit, ending mass incarceration, and single-payer healthcare in New York.

[21] His Assembly district includes a section of Astoria, which has a significant population of Muslim and Arab voters and is also the center of the socialist movement in New York City.

[23] On October 23, 2024, Mamdani announced that he would be entering the upcoming race for New York city mayor [24] following Eric Adams' federal prosecution and several investigations into his administration.

Mamdani is running on freezing rent and building housing for working families, fast and fare-free buses for riders, and free childcare for all New Yorkers.

[25] He is endorsed by the New York City chapter of the Democratic Socialists of America, UAW Region 9A, and Jewish Voice for Peace Action.

And they were opposed to this program because they were saying that now is not the time to create any kind of confusion around fare collection.”[33][34] In December 2022, Mamdani introduced a series of bills for the 2023 session called "Fix the MTA".

[36] In 2023, Mamdani co-introduced a bill that would enact a weight-based vehicle-registration fee to dissuade people from owning heavier vehicles in an effort to make streets safer.

The purpose of the bill was to fund more frequent and reliable buses to "show New Yorkers that congestion pricing will be met with better public transit options, instead of simply saddling them with higher costs or longer commutes.

[48][49] Mamdani believes that to increase public safety, what is needed is "dignified work, economic stability, and well-resourced neighborhoods," rather than policing and prisons.