This paper studies the influence of metal precursors in the CVD's catalyst synthesis of carbon nanotubes (CNTs) used as fillers in a polypropylene (PP) matrix (∼0.3 wt%). Two catalytic schemes, Fe/Al2O3 (50:50) and Ni-Fe/Al2O3 (40:10:50), were prepared to determine the influence of the reduction temperature over the characteristics and mechanical properties of CNT as PP fillers. The conversion temperature was varied to see the dependance of the CNT structure to this variable (700 °C-750 °C-800 °C). CNTs products were characterized by SEM and Raman spectroscopy. The SEM micrographs showed a sharper fiber type CNTs for the bimetallic catalyst and the Raman confirmed that better crystallites are obtain over the Fe catalyst. The Fe-PP composite presented enhanced mechanical properties when compare with Fe-Ni-PP, with tensile strength, hardness, and impact properties are higher in 16%, 9%, and 9% respectively. Other carbonaceous materials, as CNF, with less crystallinity presented poorer mechanical properties. Finally, can be stated that for the use of CNF as fillers in PP composites a Fe/Al2O3 catalyst, and a reaction temperature 700 °C-750 °C will produce a CNF with 60 nm mean diameter, is better than the use of Fe-Ni based catalysts.