The development of the wearable sensors for healthcare related applications requires mechanically stretchable, electrically conductive and biologically compatible elastomers. We have fabricated a conductive polyurethane (PU) elastomer by in situ polymerization with surface hydroxyl-modified Multi-Walled Carbon Nanotubes (MWNTs). The FT-IR and Raman spectroscopy results indicated that the successful incorporation of the MWNTs into PU macromolecules. The good dispersion of MWNTs in PU/MWNT elastomers was confirmed by transmission electron microscopy (TEM) and Raman spectroscopy. Thermogravimetric analysis (TGA) suggested improved thermal stability of the in situ polymerized PU/MWNT elastomers. The in situ polymerization with MWNTs led to a significant increase in the conductivity of PU/MWNT elastomers. The stretching facilitated the orientation of the MWNTs and further enhanced the conductivity of PU/MWNT elastomers. The in situ polymerized PU/MWNT elastomers were employed as electrodes to construct a pressure sensor demonstrating good sensitivity and consistency.