Garland attended Harvard College on a scholarship, graduating as valedictorian with an A.B. degree summa cum laude and Phi Beta Kappa in social studies in 1974. He initially wanted to become a physician, but quickly decided to become an attorney instead. Garland allied himself with his future boss, Jamie Gorelick, when he was elected the only freshman member of a campus-wide committee on which Gorelick also served. During his college summers Garland volunteered as Congressman Abner J. Mikva's speechwriter. After President Jimmy Carter appointed Mikva to the D.C. Circuit, Mikva would rely on Garland when selecting clerks. At Harvard, Garland wrote news articles and theater reviews for the Harvard Crimson and worked as a Quincy House tutor. Garland wrote his 235-page honors thesis on industrial mergers in Britain in the 1960s.
Garland then attended Harvard Law School, graduating with a J.D. magna cum laude in 1977. During law school, Garland was a member of the Harvard Law Review, serving as an articles editor from 1976 to 1977. As an articles editor, Garland assigned himself to edit a submission by Justice William Joseph Brennan Jr. on the topic of the role of state constitutions in safeguarding individual rights. Garland's correspondence with Brennan ultimately helped him win a clerkship with the justice. Garland ran for president of the Review, but lost to Susan Estrich.