The nanotwin structure and graphene (Gr)-reinforced phase can significantly enhance the mechanical properties of the material. However, there have been relatively few studies on the mechanisms underlying the strengthening resulting from the interaction between these two components in titanium–aluminum (TiAl) alloy materials. Here, molecular dynamics (MD) simulations were employed to investigate the mechanical properties and microstructural evolution of nanotwinned TiAl/Gr (nt-TiAl/Gr) composites under uniaxial loading. The study investigated the influence of Gr layer number and temperature on composite properties. Results demonstrate that the twin boundary structure interacts with graphene, enhancing mechanical properties synergistically. Relative to pure nt-TiAl, the maximum tensile strength increased by 7.42%, 24.66%, and 35.86% for varying Gr layers. Furthermore, the mechanical properties of nt-TiAl/Gr composites exhibit an inverse correlation with temperature, where maximum tensile strength decreases with temperature elevation. The synergy between Gr and the twin structure significantly inhibits dislocation diffusion and diminishes dislocation nucleation, thus improving the properties of the composite. •The synergistic effect of twin boundary and graphene significantly enhanced the properties of TiAl alloy composites.•Both the twin boundary and graphene affect the formation and propagation of dislocations.•The increase of the tensile load activates the dislocation emission and forms a large number of entangled dislocation nodes.•The mechanical properties of nt-TiAl/Gr are significantly affected by the change of temperature.