Friction stir processing (FSP) has revolutionized material science, especially with regard to improving hybrid composite materials. The importance of simulation in comprehending FSP dynamics, overcoming obstacles, and streamlining procedures is emphasized in this chapter. Researchers can obtain insights into intricate interactions by modeling material flow, temperature distribution, and microstructural changes. However, they must overcome constraints related to model complexity and resource consumption. Precision machine learning and sophisticated modeling are potential future applications. Notwithstanding these challenges, FSP understanding and optimization are much improved by simulation, which promotes further developments in hybrid composite materials.