[8][9] The Brennan Center's stated mission is to "work to hold our political institutions and laws accountable to the twin American ideals of democracy and equal justice for all.

[11] Justice Brennan's idea of a living constitution figures largely into the center's work.

[13] The Brennan Center opposes mass incarceration and produces research on causes of violent crime in the United States.

[18][19][20] The Brennan Center has represented several detainees at the Guantanamo Bay detention camp, and also U.S. citizens or legal residents held as unlawful enemy combatants.

[21] Attorneys from the Brennan Center challenged a U.S. President's authority to declare a prisoner to be an unlawful enemy combatant in the war on terror.

[22] The Brennan Center assisted in drafting and enacting the Bipartisan Campaign Reform Act of 2002 (BCRA).

[30][31][32] The Brennan Center research has also indicated that instances of voter fraud by citizens and non-citizens are very rare.

In oral arguments on December 7, 2022, the Brennan Center urged the United States Supreme Court to allow the North Carolina Supreme Court to strike down the state legislature’s congressional map for violating the North Carolina Constitution.