A novel intumescent flame retardant (IFR) poly(butylene succinate) (PBS) with an antidripping property using fumed silica as a synergistic agent was prepared. Ammonium polyphosphate, melamine, and fumed silica were added in PBS via melt blending. It was revealed that the flame retardant PBS exhibited both excellent flame retardance and antidripping properties when the three components of IFR coexisted at an appropriate proportion. The lowest total loading of flame retardant could be reduced to 17 wt % with the synergism of fumed silica, for the goal of vertical flammability (UL-94) V-0 rate. Scanning electron microscopy and X-ray photoelectron spectroscopy were employed to characterize the morphology and composition of residual char, respectively. The combustion properties and thermal degradation behavior of the IFR-PBS composites were fully evaluated, and the possible flame retardant mechanism was proposed.