In this study it was aimed to improve the fire retardant performance of halogen free flame-retardant polypropylene by increasing limiting oxygen index value. Ammonium polyphosphate, pentaerythritol, and ulexite were used to improve flame retardancy of polypropylene. Ulexite powder filled (1, 2, and 4 wt%) polypropylene composites were obtained by using a twin-screw extruder and injection molding method. Thermal, mechanical, and flame retardant performances of polypropylene composites were investigated by several characterization techniques. Limiting oxygen index value was obtained higher than 45% when ulexite was added into polypropylene at 1-4 wt%. It was observed that flame retardant additives do not change the mechanical properties considerably. The effect of ulexite addition on melting and crystallization temperatures of polypropylene-based composite is not pronounced.