Brown began studying radical feminism with Gainesville Women's Liberation (GWL), which was founded in 1968 and was the first women's liberation group in the South.^[4][5][6] She also worked with the Redstockings of the Women's Liberation Movement, developing the Redstockings Archives for Action, a repository of women's liberation history and activist resources.^[7][8][9] In 2009, GWL and Redstockings collaboratively founded National Women's Liberation (NWL) and Brown became the national organizer of the new group.^[10][11]

In 2019, Brown published Birth Strike: The Hidden Fight over Women's Work,^[12] in which she argues that the legal impediments to contraception and abortion access, rather than being discounted as products of prudish religious values, are better understood as a struggle over labor. The book argues that the ruling class, fearing the economic consequences of a declining birth rate, restricts access to contraception and abortion, intending to push more women into performing the labor of bearing and raising children. But women, she concludes, are engaged in a sort of labor strike––refusing to perform that labor in a world where they lack affordable healthcare, affordable childcare, paid work leave, job protections, and reliable male partners.

Brown was involved in the campaign to make Plan B, the "morning-after pill," available over-the-counter in the United States.

In 1999, the United States Food and Drug Administration (FDA) found Plan B safe and effective, but approved it only for prescription use.^[13] In 2001, a group of reproductive health professionals petitioned the FDA to make it available over-the-counter.^[14] The FDA eventually denied the petition in June 2006.^[15]

Brown and other NWL activists organized against the FDA.^[16] In January 2005, Brown was one of nine women arrested for a sit-in blocking access to the entrance of the FDA headquarters in Maryland, and ^[17][18] was one of the plaintiffs in a lawsuit that ultimately resulted in a federal court ruling, Tummino v. Hamburg, 936 F. Supp. 2d 162 (E.D.N.Y. 2013), requiring the FDA to make Plan B available over-the-counter, without a prescription and without age restrictions.^[19][20]

Brown and NWL continue to advocate for the expansion of access to emergency contraception, including by making it directly available on school campuses and pushing for universal health care.^[21][22]

In Gainesville, Florida, Brown co-chaired the Alachua County Labor Party for ten years.^[23][24][25] She also worked as a writer and editor for Labor Notes and is a frequent contributor to Jacobin.^[26][27]

• Brown, Jenny (2019). Without Apology: The Abortion Struggle Now. New York: Verso Books. ISBN 1788735846.
• Brown, Jenny (2019). Birth Strike: The Hidden Fight over Women's Work. Oakland: PM Press. ISBN 162963638X.
• Bradbury, Alexandra; Brenner, Mark; Brown, Jenny; Slaughter, Jane; Winslow, Samantha (2014). How to Jump-Start Your Union: Lessons from the Chicago Teachers. Detroit: Labor Notes. ASIN 0914093010.
• Brown, Jenny; Coenen, Amy; Sarachild, Kathie (2001). Women's Liberation and National Health Care: Confronting the Myth of America. New York: Redstockings. ISBN 061512187X.