The successful applications of graphene nanomaterials in nanobiotechnology and medicine as well as their effective translation into real clinical utility hinge significantly on a thorough understanding of their nanotoxicological profile. Of all aspects of biocompatibility, the hemocompatibility of graphene nanomaterials with different blood constituents in the circulatory system is one of the most important elements that needs to be well elucidated. Once administered into biological systems, graphene nanomaterials may inevitably come into contact with the surrounding plasma proteins and blood cells. Crucially, the interactions between these hematological entities and graphene nanomaterials will influence the overall efficacy of their biomedical applications. As such, a comprehensive understanding of the hemotoxicity of graphene nanomaterials is critically important. This review presents an up-to-date elucidation of the hemotoxicity of graphene nanomaterials through their interactions with blood proteins and cells, as well as offers some perspectives on the current challenges, opportunities, and future development of this important field.