Born into a working-class New Jersey home in 1966, Judy Nicastro learned the importance of political power first-hand when she and her mother suffered from funding cuts to widows' benefits in President Reagan's 1981 budget, an experience that helped shape her populist agenda as a Seattle Council Member in later years. Nicastro earned a law degree from the University of Washington in the 1990s, where she also served as Student Body President, before settling in Fremont and working for the Boeing Company as a buyer of 767 airplane parts.

In 1999, at a time of skyrocketing rent increases due to Seattle's booming economy, Nicastro won a Seattle City Council position on a renters' rights platform. This was an important issue to many Seattle residents at the time, fifty-two percent of whom were renters themselves. Nicastro served one term on City Council (1999-2003) and earned a reputation as a fiery character--outspoken, unpredictable, and brash--known for her off-the-cuff comments, verbal assaults on opponents, and continual sparring with Mayor Greg Nickels and labor union leaders. Criticized for her seemingly erratic voting record, she retorted: "I'm not a rubber stamp for anyone. I don't work for the mayor. I don't work for labor. I don't work for the affordable housing community. I work for the people." After initial doubts concerning her effectiveness, Council President Margaret Pageler praised Nicastro for her pragmatic rather than knee-jerk approach to politics, pointing out that she was "more interested in finding solutions than in being politically correct." While many cheered her actions as those of a working-class advocate for the rights of the underdog, others denounced her as a game player lacking seriousness of purpose.

During her time on the City Council, Nicastro chaired the Landlord/Tenant & Land Use Committee and served as vice-chair of the Committee of Culture, Arts & Parks as well as the Housing, Human Services & Community Development Committee. Through her committee work Nicastro helped to make changes which significantly increased Seattle renters' leverage in dealing with landlords. She sponsored a bill which strengthened landlord retaliation provisions in the Municipal Code--changing penalties from criminal to civil--and gave tenants the right to organize for the first time in Seattle history. She also pushed for Emergency Order Tenant Relocation Assistance and led the effort for an expanded rental assistance program, and she lowered parking requirements for affordable housing, making it cheaper for developers to build low-income housing. In 2002, Nicastro was the only Councilmember to oppose placing an $86 million Housing Levy on the ballot, explaining that it would provide too much money for home ownership programs rather than the people the "low income" levy was intended to help.

In addition to advocating for renters' protections and low income assistance, Nicastro became involved with small business incentives and local environmental and humanitarian affairs as well, supporting human services and homelessness funding and sponsoring and defending many issues involving civil rights, communities of color, women and domestic violence, fair labor practices, gay/lesbian/bisexual/transgendered interests, animal rights and off-leash areas, and public safety. As chair of the Land Use Committee, Nicastro was a consistent proponent of more compact urban development, especially in areas where rapid transit had been proposed.

In 2003 Nicastro was one of three council members investigated by the City Ethics and Elections Commission in the "Strippergate" scandal, accused of rezoning a Lake City strip club to allow for additional parking in exchange for campaign contributions from the Colacurcio family, who have alleged ties to Seattle's history of political corruption. The Commission investigation determined that Nicastro had accepted over $22,000 of campaign funding from Frank Colacurcio Jr. and other family members, which at least partially explains her defeat in an attempt at a second term in office.