Classical Hodgkin lymphoma (cHL) is defined by malignant Reed-Sternberg (RS) cells that recruit non-malignant immune cells into a supportive tumour microenvironment. In cHL, this is driven, in part, by genomic alterations of the 9p24.1 locus encoding the immune checkpoint ligands PD-L1 and PD-L2. Therapeutic anti-PD-1 antibodies have been developed that competitively inhibit the interaction between PD-1 and its ligands. Clinical trials of anti-PD-1 antibodies in cHL demonstrate high overall response rates but relapses still occur and new clinical challenges exist for toxicity management and response assessment. This review discusses the biological and clinical features of anti-PD-1 antibody therapy in cHL.