Talc reinforced polypropylene (PP) compounds have been used widely in injection moulded automotive interior and exterior applications such as bumper, door panels due to their cost/performance and processability. Talc has the critical role of reinforcement and nucleating agent in automotive compounds in order to enhance the stiffness/toughness balance. Due to recent developments in milling technology, talcs with high aspect ratio and reduced particle size can be generated. This proceeding enables to formulate talc reinforced PP automotive compounds having increased specific strength and reduced density as a light weighting solution for automotive industry. The rheological and crystallization behaviour of PP based automotive plastics has the critical effects on process parameters such as injection pressure, injection velocity, injection time and overall cycle time during injection moulding process. In this study, the influence of talc properties such as particle size, aspect ratio and flowability of 20% talc reinforced homo and copolymer PP was investigated by rheometric measurements. The influence of the particle size, aspect ratio on crystallinity of 20% talc reinforced homo and copolymer PP was also investigated by DSC analysis. The relationship between rheological properties, crystallization behaviours and process parameters was studied.