She began her teaching career as a lecturer at the University of Chicago from 1965 to 1966, teaching the Introduction to Modern Social Science. She then became a lecturer at Harvard University in 1967 lecturing on General Education. After becoming an assistant professor in the Harvard Graduate School of Education in 1971, she became increasingly distinguished and received tenure with the Harvard Graduate School of Education in 1988 as a full professor. Gilligan taught for two years at the University of Cambridge (from 1992 to 1994) as the Pitt Professor of American History and Institutions and as a visiting professorial fellow in the Social and Political Sciences. In 1997, she became Patricia Albjerg Graham Chair in Gender Studies at Harvard. From 1998 until 2001 she was a Visiting Meyer Professor and later visiting professor at New York University Law School.

Gilligan published what is considered one of her most influential works in 1982, after entering the dialogue regarding women and morality in the 1960s. Before she conducted her research Gilligan knew that “psychologists had assumed a culture in which men were the measure of humanity, and autonomy and rationality (‘masculine’ qualities) were the markers of maturity. It was a culture that counted on women not speaking for themselves”. To explore this theory further, Gilligan conducted her research using an interview method. Her questions centered around the self, morality and how women handle issues of conflict and choice. Her three studies that she references throughout the work were the college student study (moral development), the abortion decision study (experience of conflict), and the rights and responsibilities study (concepts of self and morality across men and women of different ages). From these studies Gilligan formed the framework for her ethics of care. Furthermore, Gilligan introduces In a Different Voice by explaining that “the different voice I describe is characterized not by gender but theme. Its association with women is an empirical observation, and is primarily through women’s voices that I trace its development. But this association is not absolute and the contrasts between male and female voices are presented here to highlight a distinction between two modes of thought and to focus on a problem of interpretation rather than to represent a generalization about either sex.” Regardless of the findings Gilligan made from her study, her ethics of care and the fuel for her study have called future researchers to broaden the scope of studies and consider intersectionality more as well.

Gilligan eventually left Harvard in 2002 to join New York University as a full professor with the School of Education and the School of Law. She was also a visiting professor at the University of Cambridge in the Centre for Gender Studies from 2003 until 2009. In 2015, Gilligan taught for a semester at New York University in Abu Dhabi.

Best known for her work, In a Different Voice (1982), Gilligan studied women’s psychology and girls’ development and co-authored or edited a number of texts with her students. She contributed the piece “Sisterhood Is Pleasurable: A Quiet Revolution in Psychology” to the 2003 anthology Sisterhood Is Forever: The Women’s Anthology for a New Millennium, edited by Robin Morgan. She published her first novel, Kyra, in 2008.

In her book In a Different Voice Gilligan presented her ethics of care theory as an alternative to Lawrence Kohlberg’s hierarchal and principled approach to ethics. In contrast to Kohlberg, who claimed that girls, and therefore also women, did not in general develop their moral abilities to the highest levels, Gilligan argued that women approached ethical problems differently from men. According to Gilligan, women’s moral viewpoints center around the understanding of responsibilities and relationship whilst men’s moral viewpoints instead center around the understanding of moral fairness, which is tied to rights and rules. Women also tend to see moral issues as a problem of conflicting responsibilities rather than competing rights. So whilst women perceive the situation as more contextual and narrative, men define the situation as more formal and abstract. In her 2011 article about In a Different Voice, Gilligan says she has made “a distinction [she] ha[s] come to see as pivotal to understanding care ethics. Within a patriarchal framework, care is a feminine ethic. Within a democratic framework, care is a human ethic. A feminist ethic of care is a different voice within a patriarchal culture because it joins reason with emotion, mind with body, self with relationships, men with women, resisting the divisions that maintain a patriarchal order”. She calls the different moral approaches “ethics of care” and “ethics of justice” and recognizes them as fundamentally incompatible.