<p>A comparative analysis was conducted on the equiatomic MoNbVTi model high-entropy alloy and its carbon-incorporated counterpart, (MoNbVTi)₉₅C₅. The research indicates that the presence of secondary carbides at grain boundaries exerts varying effects on the mechanical properties of the (MoNbVTi)₉₅C₅ alloy under different temperature conditions. At room temperature, these carbides manifest as a brittle phase, which detrimentally affects both the strength and plasticity of the alloy. Conversely, under high-temperature conditions, the carbon-containing (MoNbVTi)₉₅C₅ alloy demonstrates enhanced strength and improved compressive plasticity. It is proposed that, in thermal environments, unique physicochemical interactions occur between the carbides and the matrix, leading to the formation of ceramic-strengthening phases that contribute to an increase in alloy strength. Density functional theory (DFT) simulations estimated an upper limit of ~ 0.85 at.% for carbon concentration in the bulk phase, revealing carbide formation at grain boundaries. Future research will focus on in situ characterization of carbide compositions/properties at elevated temperatures, exploring the intrinsic correlation between carbon content and alloy mechanical behavior, and elucidating the underlying mechanisms.</p>