Thermophysical properties play a crucial role in controlling the melt pool dimensions in metal additive manufacturing (AM). It is, therefore, imperative to understand the impact of thermophysical properties on the melt pool dimensions for critical materials such as nickel-based superalloys. In this paper, a three-dimensional analytical model is used to predict the steady-state melt pool dimension over a range of process parameters for several nickel-based superalloys. The effects of composition, in terms of the thermophysical properties, on the melt pool dimensions are also studied. The results show that the melt pool dimensions correlate well with the liquidus temperature, density, and thermal conductivity of the alloy. By exploring the impact of process parameters and compositions on the melt pool dimension evolution, a framework can be established to maintain the desired melt pool dimensions during the fabrication of functionally- graded parts with different alloys belonging to the same material class.