Piezoresistive strain sensing of multiwalled carbon nanotube (CNT)reinforced polymer nanocomposites considering the effect of agglomeration is experimentally investigated. Thermoplastic polyurethane is used as composite matrix with melt mixing method for fabricating the nanocomposite. The electrical resistance of the nanocomposite specimens is measured by a designed electrical circuit in conductivity and piezoresistivity tests. The electrical resistance of the nanocomposite decreases by a nonlinear relation when CNT is added up to 1.5 wt% and has an inverse behavior after this weight fraction. Comparison between scanning electron microscope images