Frankfurt was born David Bernard Stern at a home for unwed mothers in Langhorne, Pennsylvania, on May 29, 1929, and did not know his biological parents.

Shortly after his birth, he was adopted by a middle-class Jewish family and given a new name, Harry Gordon Frankfurt.

His adoptive parents, Bertha (née Gordon) and Nathan Frankfurt, a piano teacher and a bookkeeper, respectively, raised him in Brooklyn and Baltimore.

His most influential work, however, is on freedom of the will (on which he wrote numerous important papers[9]) based on his concept of higher-order volitions and for developing "Frankfurt cases" (also known as "Frankfurt counter-examples", which are thought experiments designed to demonstrate the possibility of situations in which a person could not have done other than he/she did, but in which our intuition is to say nonetheless that this feature of the situation does not prevent that person from being morally responsible).

[13] He was a Visiting Fellow of All Souls College, Oxford University;[14] he served as president, Eastern Division, American Philosophical Association;[15] and he received grants and fellowships from the Guggenheim Foundation, the Andrew Mellon Foundation and the National Endowment for the Humanities.

[17][18] In the academic literature, caring is often understood as a subjective attitude in contrast to importance as an objective factor.

[19][20][21] Frankfurt defends a different perspective on this issue by arguing that caring about something makes this thing important.

[16][21] Yitzhak Benbaji terms this relation between caring and importance "Frankfurt's Care-Importance Principle".

In one example, the agent follows a charlatan's health advice to avoid a certain type of food.

Benbaji argues that this constitutes a counterexample because the person cares about avoiding this food even though it has no impact on their health or their well-being.

[22][23] However, there is wide disagreement, both within the academic discourse and between different cultures about what the essential features of personhood are.

[24] One influential and precisely formulated account of personhood is given by Frankfurt in his "Freedom of the Will and the Concept of a Person".

Various of Frankfurt's examples of such cases involve some forms of akrasia in which a person acts according to a first-order desire that he/she does not want to have on the second order.

Frankfurt argues that, in this case, Allison is morally responsible for walking her dog even though she lacked the ability to do otherwise.

[31][34] This line of thought has led Frankfurt to advocate a form of compatibilism: If free will and moral responsibility do not depend on the ability to do otherwise, then they could even exist in a fully deterministic world.

He started taking piano lessons from an early age, initially from his mother who hoped that he might pursue a career as a concert pianist.

Frankfurt continued to play piano and receive lessons throughout his life, alongside his philosophical career.

According to Frankfurt, becoming a professor of philosophy was acceptable to his mother, seeing as it was "close enough" to her other ambition for him, which was to become a rabbi.

[36] Frankfurt died of congestive heart failure in Santa Monica, California, on July 16, 2023, at age 94.