The article presents data on synthesis, identification, computer modelling and biocompatibility of graphene oxide functionalised with L-methionine (GFM). In the framework of our research, graphene oxide synthesised using Hammers' method was modified through amidation reaction. The characterisation of the compound was performed using various physicochemical techniques, such as X-ray diffraction, X-ray photoelectron spectroscopy, infrared, Raman spectroscopy, thermogravimetric analysis, scanning electron microscopy, and high-resolution transmission electron microscopy. Investigation of biocompatibility included experiments on erythrocytes haemolysis, platelet aggregation, photodynamic and antiradical activity studies, binding to human serum albumin, geno- and cytotoxicity. Moreover, using density functional theory and molecular dynamics approaches, structural and dynamic characteristics of a GFM–water binary system were obtained.