The grain size of materials is significantly reduced by dynamic recrystallization (DRX), which improves the properties and performance of the materials, and it helps to extend the applications further. DRX behavior of the composite materials is greatly affected by the addition of reinforcement to the matrix due to the heterogeneous temperature of the composite. Therefore, the present investigation aims to study the DRX behavior of hot upset sintered Al-B4C composite with various percentages of B4C content (2, 4 and 6 wt.% of B4C) with 90% of initial relative density. Hot upset tests were performed for various temperatures (300-500 °C) and strain rates (0.1-0.3 s−1). The DRX grain size was significantly altered not only with deformation conditions but also with the addition of reinforcement in the matrix. The fracture surface of the sintered composite was analyzed for various compositions. Ductile fracture is observed in the 2 and 4 wt.%B4C content, and ductile and brittle fractures were observed in the 6 wt.%B4C composites. DRX models were established between grain size and deformation conditions for various compositions to predict the grain size, and the developed models were validated. The measured and calculated DRX grain size absolute error and mean absolute error were not exceeding 8.9 and 7.7%, respectively.