Greenfield is the founding director and counsel of TEACH NYS, and prior to his election served as the executive vice president of the Sephardic Community Federation. As Director and Counsel of TEACH NYS, Greenfield organized statewide advocacy campaigns that resulted in private and public school parents receiving tax breaks and private schools receiving more government assistance. Greenfield served as deputy director of finance in Senator Joseph Lieberman's 2004 presidential campaign. Prior to that, he had a stint as chief of staff to Assemblyman Dov Hikind. Greenfield was ranked as the 51st most powerful New Yorker in City & State's Power 100 list in 2014.
On January 7, 2010 Greenfield announced his candidacy on the Zev Brenner radio show to replace Simcha Felder. Felder announced his resignation after accepting the post as the new deputy comptroller for accounting and budget under John Liu. Greenfield received endorsements from U.S. Senator Joseph Lieberman, then-Mayor Michael R. Bloomberg, former Mayor Ed Koch, and State Senators Carl Kruger, Martin J. Golden. He received the support of council members Domenic Recchia, Lewis Fidler, Michael C. Nelson, and Vincent J. Gentile, as well as the backing of the Kings County Conservative Party, Democratic county leader Vito Lopez, and Citizens Union. He was elected in his first term by his Brooklyn colleagues to co-chair the Brooklyn delegation and serve as their representative on the Budget Negotiating Team of the New York City Council. He later became the chair of the Land Use Committee of the New York City Council. Greenfield has appeared as a commentator on many national news shows including Fox & Friends and is a frequent political commentator in The New York Times and The Wall Street Journal. Greenfield is considered a political moderate in a liberal New York City Council. Greenfield authored a law that banned the Department of Sanitation from placing hard-to-remove stickers on vehicles that were parked on the wrong-side of the street. He co-authored a law that requires the Department of Education to notify parents and teachers about potentially harmful polychlorinated biphenyl in classrooms. Greenfield also introduced a law that would stop New York City from towing cars for unpaid parking tickets and instead boot the car. Greenfield's proposed legislation was adopted by the New York City Council Department of Finance as a pilot program in June 2012. Greenfield is also the author of the Vision Zero legislation that lowers the default speed-limit in New York City to 25 miles per hour. This legislation is the lynchpin of Vision Zero and is widely considered to be the key strategy behind saving lives by reducing traffic accidents in New York City. Greenfield voted against a 2010 bill that required the City Clerks office to post on its website, and hand out at its office, information on where exactly in the U.S. and the worldsame sex couples are able to get married. Greenfield is a long-time advocate for increased government funding for public and non-public schools. In July 2017, he announced that he would not be seeking a third term, and would instead be taking over as CEO of the Metropolitan Council on Jewish Poverty.
Personal life
Greenfield is Orthodox Jewish and is a member of the R' Landau's Synagogue in the Midwood, Brooklyn.
