Carter launched a campaign against a planned waste facility; it was slated to be built in her neighborhood and would process 40 percent of New York's municipal waste - although the same area already handled as much of the City's commercial waste. Her organizing helped defeat the siting of that waste facility. It catalyzed Carter to establish and direct the non-profit environmental justice solutions organization Sustainable South Bronx in 2001. She led the organization until 2008 and considered her most significant accomplishment to be her role in changing the lives of people who took part in her organization's Bronx Environmental Stewardship Training (BEST) program because of the many lives she could positively impact through the program. In 2007, Carter co-founded Green for All with Van Jones, an organization dedicated to a green economy focusing on lifting people out of poverty, highlighting her passion for serving others and entrepreneurial skills. For her work, in the New York Times, she called Carter "The Green Power Broker" and "one of the city's best-known advocates for environmental justice" in 2008. She currently provides consulting through her consulting firm, Majora Carter Group, LLC, where she provides expertise on environmental justice and urban revitalization strategies. In the role, she helps clients unlock potential through green economic methods and approaches. Additionally, she is a Lecturer at Princeton University (2021-present).

Carter's expertise has earned her extensive recognition, from several TED Talks to appearances on Discovery Communications' Science Channel, HBO's The Black List, and advertisements for Honda, Intel, and Visa, among others. Additionally, she co-hosted The Green, a TV series on the environment, from 2007 to 2010 and co-produced The Promised Land pilot episode on the public radio with Marge Ostroushko in 2008, which won a grant from the Corporation for Public Broadcasting. Carter has also produced written works on urban issues, including the urban heat island effect. In 2022, she released her first book, Reclaiming Your Community: You Don't Have to Move Out of Your Neighborhood to Live in a Better One. Carter has also received several awards, including the 2024 Commendation for Outstanding Teaching at Princeton University, the 2020 Edmund N. Bacon Urban Design Award, and the 2017 Visionary Leadership Award in Arts & Ideas, among several others.

Carter recounts that one of the lowest points of her career was her unsuccessful run for NY City Council. However, she now views her loss in politics as a "blessing in disguise" because it spurred her to create SSBx, which has had more influence than a NYC Council seat would have (2010).