The amount of generated recycled polypropylene (RPP) has been increasing year by year with the widespread use of polypropylene (PP) packaging materials. An arylamide derivative β-nucleating agent (TMB-5) was used to nucleate RPP/inorganic filler composites. The effect of TMB-5 on the crystallization behavior and melting characteristics of different kinds of RPP/inorganic filler composites were compared by virtue of differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WAXD). The results indicated that the industrial grade inorganic fillers had no obvious effects on the crystallization behavior and crystal form of RPP, while TMB-5 not only significantly increased the crystallization temperature of RPP, but also induced a large number of β-crystals. The effective synergy between the reinforcement of rigid fillers and the toughening of β-phase could be achieved through preparing RPP/inorganic filler composites with high β-phase content. As a result, filled RPP composites with high mechanical properties as good as polypropylene (PP) could be obtained.