Nozick was born in Brooklyn, the son of a Jewish entrepreneur from the Russian shtetl who had been born with the rabbinical name of Cohen. Nozick was married to the poet Gjertrud Schnackenberg. He died in 2002 after a prolonged struggle with cancer. He is interred at Mount Auburn Cemetery in Cambridge, Massachusetts.

Nozick was educated at Columbia (A.B. 1959, summa cum laude), where he studied with Sidney Morgenbesser, at Princeton (Ph.D. 1963), and Oxford as a Fulbright Scholar.

Nozick's Anarchy, State, and Utopia (1974), which received a National Book Award, argues among other things that a distribution of goods is just if brought about by free exchange among consenting adults and from a just starting position, even if large inequalities subsequently emerge from the process. Nozick appealed to the Kantian idea that people should be treated as ends (what he termed 'separateness of persons'), not merely as a means to some other end. Nozick here challenges the partial conclusion of John Rawls's Second Principle of Justice of his A Theory of Justice, that "social and economic inequalities are to be arranged so that they are to be of greatest benefit to the least-advantaged members of society." Anarchy, State and Utopia claims a heritage from John Locke's Second Treatise on Government and tries to base itself upon a natural law doctrine. Locke only relied on natural law as God-given to counteract the King of England's claim to divine right and thus claim to all the property of England. Nozick suggested, again as a critique of utilitarianism, that the sacrosanctity of life made property rights non-negotiable. This principle has served as a foundation for many libertarian pitches into modern politics. Most controversially, Nozick argued that a consistent upholding of the libertarian non-aggression principle would allow and regard as valid consensual/non-coercive enslavement contracts between adults. He rejected the notion of inalienable rights advanced by most other libertarian academics, writing in Anarchy, State and Utopia that the typical notion of a "free system" would allow adults to voluntarily enter into non-coercive slave contracts.

In Philosophical Explanations (1981), which received the Phi Beta Kappa Society's Ralph Waldo Emerson Award, Nozick provided novel accounts of knowledge, free will, personal identity, the nature of value, and the meaning of life. He also put forward an epistemological system which attempted to deal with both the Gettier problem and those posed by skepticism. This highly influential argument eschewed justification as a necessary requirement for knowledge.

Nozick's Four Conditions for S's knowing that P were:

(1) P is true

(2) S believes that P

(3) If it were the case that (not-P), S would not believe that P

(4) If it were the case that P, S would believe that P

Nozick's third and fourth conditions are counterfactuals. Nozick calls his theory the "tracking theory" of knowledge. Nozick believes that the counterfactual conditionals bring out an important aspect of our intuitive grasp of knowledge: For any given fact, the believer's method must reliably track the truth despite varying relevant conditions. In this way, Nozick's theory is similar to reliabilism. Due to certain counterexamples that could otherwise be raised against these counterfactual conditions, Nozick specified that: