Highly stretchable elastomeric multiwall carbon nanotubes – poly (glycerol sebacate) (MWCNT-PGS) nanocomposites were prepared by mixing conductive multiwall carbon nanotubes (MWCNTs) with PGS prepolymer and curing at 120 °C. The incorporation of conductive filler increases the matrix crosslinking density and mechanical stiffness without loss of the flexibility and elasticity of the polymeric network with low mechanical hysteresis behaviour. The percolation threshold for the electrical conductivity was found to be ∼1 wt% of MWCNTs. The piezoresistive behaviour of the prepared samples shows a negative gauge factor (GF) between −0.5 and −0.8 under uniaxial tensile stress, probably due to geometrical factors, whilst under 3-point bending the calculated GF values were positive and a maximum GF = 42 was achieved for the samples with 2 wt% MWCNTs. Overall, the unique property combination between the MWCNTs and the PGS make them potentially suitable for the development of large deformation piezoresistive sensors, especially for biomedical engineering applications, flexible and wearable devices.