A study on the electrical behavior of polymer composites based on multi-walled carbon nanotubes (MWCNT) under the application of hydrostatic pressure up to 9 GPa and at room temperature is reported. A higher resistance, with values of order of kΩ, is demonstrated for MWCNT with an aspect ratio R9GPa/Rint ≈7. Our observations also show that pressure induced a structural change of the MWCNT to an ellipsoid shape at P ∼ 1–1.5 GPa—a measurement that correlates rather well with theoretical predictions. By direct and reverse high-pressure measurements of resistance, as well as current-voltage characteristics, we have identified the reversibility of electrophysical properties. Our observations suggest that the polymer composite based on MWCNT is a promising material for pressure sensing devices.