This paper presents an experimental investigation into the one-dimensional piezoresistive behavior of 3D-printed conductive carbon-fiber polylactic acid (PLA) structural samples. The ability to accurately characterize the piezoresistive properties of such materials is crucial for their application in various fields, including flexible electronics, smart structures, and sensing systems, to name but a few. This study involves the fabrication of carbon-fiber PLA composite samples using a 3D-printing technique and the subsequent testing under different mechanical loading conditions. A comprehensive experimental setup is established to measure the electrical resistance changes in the samples corresponding to applied strain. The obtained data are analyzed to determine the piezoresistive coefficients and investigate the linearity and repeatability of the material's response. The results reveal a clear relationship between the applied strain and the resistance change, demonstrating the piezoresistive behavior of the 3D-printed conductive carbon-fiber PLA structural samples. The findings contribute to a better understanding of the material's sensing capabilities and pave the way for its utilization in various applications requiring strain sensing and structural health monitoring. Further research is warranted to optimize the fabrication process, investigate the effects of different printing parameters, and explore the material's potential for integration in advanced sensing systems and smart structures in various operating scenarios.