The number of incarcerated people in the United States with mental health treatment needs is inexcusably and unconscionably high. The authors argue that while the justice reform movement has made some laudable efforts to address the overincarceration of people with mental health treatment needs, these efforts have focused almost entirely on the front end of the criminal legal system (e.g., arrest and jail diversion), as well as problem-solving courts and alternative sentencing programs. And while plenty of work to prevent incarceration remains to be done, the authors seek to shine a bright light on how the post-conviction mechanisms of compassionate release, clemency, and sentencing review must be used—in some instances reimagined—to advance decarceration for people with mental health treatment needs in federal and state prison systems. The authors call on decision-makers to take a bold and expansive view of release for those whose incarceration no longer serves the interest of justice, while also recognizing that further education and advocacy are needed to overcome the conflation and sensationalizing of mental illness and violence. Concluding that prison will never be a good environment to meaningfully address mental health treatment needs, the authors contend that there must be a deeper moral reckoning with—and more revulsion against—the warehousing of people struggling with mental health treatment needs in the United States.