In the seven years before launching its criminal procedure “revolution,” the Warren Court protected federal criminal defendants’ rights through decisions exercising its supervisory authority. The first of these, United States v. Offutt, 348 U.S. 11 (1954), overturned a lawyer’s criminal contempt conviction based in part on the Court’s “supervisory authority over the administration of criminal justice in the federal courts.” Justice Frankfurter’s Offutt opinion referred to his earlier one in McNabb v. United States, 318 U.S. 332 (1943), which is credited as the first to invoke the Court’s “supervisory authority” over the administration of federal criminal justice, a power that is not limited by the Constitution’s “minimal historic safeguards.” In the succeeding years, the Warren Court used this power in a range of federal criminal cases involving, among other things, a defendant’s right to elicit an informant’s identity, the inadmissibility of inferences from a witness’s invocation of the self-incrimination right, excessive publicity, and improper investigative methods. Although the early Warren Court was vague about the source and parameters of its supervisory authority, it was nonetheless confident in its possession of this power, in the breadth of this power, and in the obligation to employ it. This Article briefly describes the Court’s “supervisory authority” decisions leading up to Offutt, then discusses Offutt and its aftermath. It describes the initial significance of supervisory authority following Offutt, its declining role once the Warren Court turned its attention to the Bill of Rights provisions, and then its erosion by later Courts. It asks whether supervisory authority might have sustained a more important role in federal criminal procedure if it had been more firmly entrenched during the Warren Court era.