Conductive polymer composites (CPCs) show piezoresistive behavior, which can be used for both strain sensing and material structural health monitoring (SHM). During deformation, the electrical resistance changes due to altering of the conductive network. Compared with other strain sensors based on capacitive or piezoelectric materials, CPC based sensors have advantages like facile fabrication, tunable piezoresistive sensitivity and capability of sustaining high level of stress/strain. However, most CPC strain sensors show non-linear resistivity increase against strain, because of the electrical conduction mechanism. Higher sensitivity and better linearity are difficult to achieve simultaneously. When the filler content is slightly above the percolation threshold, high sensitivity but poor linearity is usually observed. Higher filler content can help to improve the linearity but at the same time significantly reduces sensitivity. In this work, we report a facile method to tune the piezoresistive behavior of poly(vinylidene fluoride) (PVDF) / carbon nanotube (CNT) composites by adding a second commercially available polymer (poly(methyl methacrylate) (PMMA, amorphous) or poly(butylene succinate) (PBS, partially crystalline)). PMMA and PBS are miscible with PVDF in the melt state and the crystallization of PVDF and PBS can finally induce phase separation between PVDF crystalline and PVDF/PMMA amorphous phases or PVDF and PBS crystalline and PVDF/PBS amorphous phases during cooling. The addition of PMMA or PBS simultaneously improves electrical conductivity, toughness and the piezoresistive behavior. The blend composites show both higher sensitivity at low strains and better linearity compared to pure PVDF/CNT composites with comparable electrical resistivity. This phenomenon is due to the improved CNT dispersion and the changed composite microstructure. The addition of a second polymer could also be used for other polymer matrices for a broader SHM application.