Mallet finger injuries are a common presentation in the emergency department. These injuries result from a forced flexion at the distal interphalangeal joint (DIPJ) that causes extensor tendon disruption, and possibly bone avulsion, at the base of the distal phalanx. This article describes the anatomy, mechanisms, classification and assessment of mallet finger injury. It reviews different types of splints used in the conservative management of closed tendinous mallet finger injury and discusses the latest evidence regarding immobilisation methods and treatment duration. Maintaining the DIPJ in extension during treatment is essential, so the article stresses the importance of patient adherence to treatment. © 2020 RCN Publishing Company Ltd. All rights reserved. Not to be copied, transmitted or recorded in any way, in whole or part, without prior permission of the publishers.