A study has been made of the thermal, X-ray diffraction, and dynamic mechanical characteristics of polypropylene (PP1330, a copolymer containing 22% ethylene) filled with wollastonite. Various levels of β-form crystallinity were produced in the PP by mixing in varying amount of wollastonite. It has been found that all the wollastonite-filled samples contain both the α-and the β-forms, and four melting transitions were observed instead of only two of the unfilled PP on the DSC scan. The conversion of the β-to the β-form on heating has been observed. The relative amount of the β-form in the samples was measured from WAXS data by the K value. The K value obtained increases with increasing wollastonite content. Dynamic mechanical measurements showed an increase in the magnitude of the damping in the high-temperature region for the wollastonite-filled PP and the contribution from the filler-matrix boundary. Wollastonite acted as both a reinforcement and a β-nucleator for PP.