She also worked in the United States Department of Justice during the Clinton administration, including in the Civil Rights Division and Office of Legal Policy.

She later served as chief nominations counsel to Vermont Senator Patrick Leahy before returning to the Department of Justice during the Obama administration, working as deputy associate attorney general and a counselor to then-Attorney General Eric Holder.

[3] From August 2017 to November 2019, Greenfeld served as chief counsel to Hawaii Senator Mazie Hirono.

In 2020, she was special counsel to the Senate Committee on the Judiciary during the confirmation process of Amy Coney Barrett.

Greenfeld's nomination ultimately stalled in the Senate and was returned to President Biden on January 3, 2022.