Polymer foams with porous structures have many attractive features. Integrating nanomaterials into the “passive” porous polymers can result in functional nanocomposites with unique advantages. In this project the characteristics of porous nanocomposites, made of polydimethylsiloxane (PDMS) and carbon nanotubes (CNTs), for piezoresistive pressure sensing applications were evaluated. The CNTs, at the percolation threshold of 3.5 wt%, were used to increase the conductivity of the host polymer. The open-pore samples were produced with a simple scaffolding method using common granulated sugar and hot water bath. The porosity directly affected the Young’s modulus and the density of the porous structure, with a higher porosity resulting in a softer and lighter material. Counter to the common evidence, the porous samples showed a reduction in piezoresistive sensing performance when used as pressure sensor materials. Foam morphology inspection and sensing analysis suggested that the effective deformation of the overall porous structure was mitigated by the collapsing of the open pores. The characterization of the 70%-porosity samples showed clear benefits of reduced stiffness (74.4% and 88.4% reductions in tensile and compressive Young’s moduli, respectively) and lower weight (56.9% reduction in material density), with a reduced sensitivity of 30.1% from their solid counterparts. Our investigation suggests that when a porous material is considered for sensing applications, a comprehensive evaluation of compositions-mechanical-structural-sensing behaviors is warranted. This project provides an insightful perspective on functional materials research, especially on the engineering of active polymer foams with specifically desired properties for various applications.