Slaughter is a 1976 graduate of St. Anne's-Belfield School in Charlottesville, Virginia. She received her B.A. from the Woodrow Wilson School at Princeton University in 1980, where she graduated magna cum laude and received a certificate in European cultural studies. Mentored by Richard H. Ullman, she won the Daniel M. Sachs Memorial Scholarship, one of Princeton's top honors, which provides for two years of study at Worcester College, Oxford University. After receiving her M.Phil. in International Affairs from Oxford University in 1982, she studied at Harvard Law School and graduated cum laude with a J.D. in 1985. She continued at Harvard after graduation as a researcher for her academic mentor, the international Lawyer Abram Chayes. In 1992, she received her D.Phil. in International Relations from Oxford.

She has received many awards for her work over the years such as: the Woodrow Wilson School R.W. van de Velde Award, 1979; the Thomas Jefferson Medal in Law, University of Virginia and Thomas Jefferson Foundation, 2007; Distinguished Service Medal, U.S. Secretary of state 2011; Louis B. Sohn Award for Public International Law, American Bar association, 2012.

In the 1980s, as a student, Slaughter was part of the team headed by Professor Abram Chayes that helped the Sandinista government of Nicaragua bring suit against the United States in the International Court of Justice for violations of international law, in the case Nicaragua v. United States (1986).

Slaughter served on the faculty of the University of Chicago Law School from 1989–1994 and then as J. Sinclair Armstrong Professor of International, Foreign, and Comparative Law on the faculty of Harvard Law School from 1994 to 2002. She then moved to Princeton to serve as dean of the Woodrow Wilson School, the first woman to hold that position. She held that post from 2002 to 2009, when she accepted an appointment at the US State Department. During the academic year 2007–2008, Slaughter was a visiting fellow at the Shanghai Institute for International Affairs. In 2011, she returned to Princeton as a professor.

Slaughter was Director of the International Legal Studies Program at Harvard Law School from 1994–2002, and a Professor at Harvard's Kennedy School of Government from 2001–2002.

As a scholar, Slaughter has had a focus on integrating the study of international relations and international law, using international relations theory in international legal theory. In addition, she has written extensively on European Union politics, network theories of world politics, transjudicial communication, liberal theories of international law and international relations, American foreign policy, international law, and various types of policy analysis. She has published four books: International Law and International Relations (2000), A New World Order (2004), The Idea that is America: Keeping Faith with our Values in a Dangerous World (2007), and The Crisis of American Foreign Policy: Wilsonianism in the Twenty-first Century (with G. John Ikenberry, Thomas J. Knock, and Tony Smith) (2008), as well as three edited volumes on international relations and international law, and over one hundred extended articles in scholarly and policy journals or books.

From 2002 to 2004, Slaughter served as President of the American Society of International Law.

Slaughter is an experienced author and Editor, having worked on eight books, including A New World Order (2004); The Idea That Is America: Keeping Faith with Our Values in a Dangerous World (2007); Unfinished Business: Women, Men, Work, Family (2015); her latest work The Chessboard and the Web: Strategies of Connection in a Dangerous World (2017), and countless scholarly articles. Her most popular piece to this day is still her article in The Atlantic, titled "Why Women Still Can’t Have it All", which addressed the difficulties women still face in finding a balance between a fulfilling career and family life. This contribution revived a national debate over gender equality in the 21st century.

In July 2005, Slaughter wrote in the American Journal of International Law about the responsibility to protect (R2P) that:

In her 2006 Levine lecture at Fordham University, Slaughter called the R2P "the most important shift in our conception of sovereignty since the Treaty of Westphalia in 1648," and founded it in the Four Freedoms speech by President Roosevelt. She referred to a speech by Kofi Annan, in which he saw that the United Nations had come to a "fork in the road" and in her words "that it was time to decide how to adapt the institution to not the world of 1945 but the world of 2005".

On 23 January 2009, U.S. Secretary of State Hillary Clinton announced the appointment of Slaughter as the new Director of Policy Planning under the Obama administration. Slaughter was the first woman to hold this position.

At the State Department, Slaughter was chief Architect of the Quadrennial Diplomacy and Development Review whose first iteration was released in December 2010. The QDDR provided a blueprint for elevating development as a pillar of American foreign policy and leading through civilian power. Commenting upon the skepticism that often greets such reports, and reiterating Secretary Clinton's strong Desire that the QDDR become an essential part of the State Department policy process, Slaughter said: "I'm pretty sure you're thinking, 'I've heard this before,' [a big plan to change the way a government agency works] But this is different." Slaughter received the Secretary's Distinguished Service Award for exceptional leadership and professional competence, the highest honor conferred by the State Department. She also received a Meritorious Honor Award from the U.S. Agency for International Development for her outstanding contribution to development policy.

On 25 August 2011, she was roundly criticized by Matt Welch, who sorted through many of Slaughter's prior op-eds and concluded that she was a "situational constitutionalist".

Slaughter's article titled "Why Women Still Can't Have it All" appeared in the July/August 2012 issue of The Atlantic. In the first four days after publication, the piece attracted 725,000 unique readers, making it the most popular article ever published in that magazine. In the same period, it received over 119,000 Facebook "Recommends," making it by far the most "liked" piece ever to appear in any version of the magazine. Within several days, it had been discussed in detail on the front page of The New York Times and in many other media outlets, attracting attention from around the world. Although Slaughter originally tried to call the article "Why Women Can't Have it All Yet," she has since stated that it was a mistake to use the phrase "Have it All" in general. In 2015, Slaughter clarified that she hoped to stimulate a discussion about a wide range of working mothers, not only those in prestigious or lucrative careers.

Slaughter was named President and CEO of the think-tank New America in 2013. In 2017, The New York Times alleged that Slaughter had closed the Open Markets research group and dismissed its Director Barry Lynn because he had criticized Google, a major donor of New America, and called for it to be broken up. Slaughter denied that Open Markets was closed because of pressure from Google and said Lynn was dismissed because he had "repeatedly violated the standards of honesty and good faith with his colleagues." New America co-chair Jonathan Soros wrote in a letter that Google had neither "attempted to interfere" nor "threaten[ed] funding" over Open Markets research critical of monopolies. In a letter to New America's board and leadership, 25 former and current New America fellows said though they had "never experienced any efforts by donors or managers at New America to influence [their] work," they "were troubled by the initial lack of transparency and communication from New America's leadership" and "remained deeply concerned about this sequence of events".

In a 11 November 2014 piece entitled What Happened to the Humanitarians Who Wanted to Save Libyans With Bombs and Drones?, Glenn Greenwald denounced her and her policies:

The article in The Atlantic became the basis of the 2015 book Unfinished Business: Women Men Work Family. The book argues that a number of challenges remain for the women's movement in the US. It allows her to expands on her position in the article and respond to her critics. In Unfinished Business, she attempts to create a framework to understand the problems faced by all working parents, not just women. She also discusses US public policy and declares that without paid maternity leave, affordable childcare, the right to part-time work, job security for pregnant employees and better enforcement of discriminatory laws both men and women will continue to suffer. Slaughter urges a focus on the value of work being done, not on the traditional gender roles. She states that western notions of masculinity should be challenged before women imprison men to the crippling gender roles women have been fighting to escape from. Slaughter believes that men and women must acknowledge the damaging social system in place hindering their ability to make money while simultaneously caring for their families. When this system is realized they must work together to push the boundaries of traditional gender roles and create an impactful, positive change. Ultimately, Slaughter calls for a change in the workplace policies which affect both men and women. She argues that that embracing a parental role, instead of a gendered one is crucial for the success of Future families. One step toward gender equity that it advocates is empowering men to re-envision their lives and embrace the roles of engaged fathers, sons and caregivers.