In this work, synthetic talc was used as catalyst and filler aiming to obtain waterborne polyurethane (WPU) nanocomposites by in situ polymerization. Filler was used both in gel and in powder forms in order to compare its effects into the WPU matrix. The use of synthetic talc as filler is interesting due to the possibility of hydrogen bond formation between WPU chains/Si-O-Si and OH groups in synthetic talc edges promoting changes in physical, mechanical and thermal properties. Moreover, WPUs are environmentally friendly polymers replacing organic solvents by water as dispersion medium reducing pollutant emission in the atmosphere. Material structure analyzed by FTIR evidenced that it is possible to synthesize WPU using synthetic talc as catalyst and proved hydrogen bonding formation between synthetic talcs and WPU matrix. Synthetic talcs were well dispersed even with higher filler content, as supported by XRD, TEM, FESEM and AFM analyses. Thermal and mechanical performance was improved with synthetic talc fillers' addition in order to obtain WPU nanocomposites. Also, T-g of WPU nanocomposites was affected by fillers' addition as presented by DSC corroborating synthetic talc good dispersion as evidenced by XRD and TEM analyses. Synthetic talcs used as catalyst/filler resulted in nanocomposites with superior thermal and mechanical properties being a new path to utilize synthetic talcs to obtain multifunctional materials.