Unlike consequentialists, retributivists condemn bargain justice—plea bargains and immunity deals—as violating a number of conditions of just punishment. While the difficulties prosecutor initiated bargaining poses for prisoners in a consequentialist system of criminal justice is well known under the rubric of the prisoner’s dilemma, this Article introduces the difficulties prisoner-initiated bargaining poses for prosecutors in a retributivist system of criminal justice. Applying four central principles of retributivism to a prisoner-initiated proposal offering inculpatory testimony on the prisoner’s confederates in exchange for immunity demonstrates that each principle paradoxically requires, and is violated by, both acceptance and nonacceptance of the offer. Retributivism’s conflicting principles generate a moral dilemma—the Prosecutor’s Dilemma—in which no matter what a prosecutor does in response to the offer, retributivism’s principles will be violated. According to the means preferred by retributivists themselves to resolve conflicts among principles, the Prosecutor’s Dilemma is to be resolved by not accepting the offer and punishing neither the prisoner nor her confederates. Though perhaps theoretically sound, the resolution is a practical disaster. It allows prisoners to self-immunize merely by tendering a dilemmatic immunity offer. While the resolution perhaps reduces retributivism to the point of absurdity by disabling retributivism from justifying punishment of either the prisoner or her confederates, without the resolution of the Prosecutor’s Dilemma retributivism remains internally inconsistent. As a result, the Prosecutor’s Dilemma supplies an indirect defense of bargain justice.