A novel reinforcement of mineral-impregnated carbon fiber (MCF) composite has been introduced to replace traditional steel or fiber-reinforced polymer (FRP) reinforcements, primarily attributed to its high-temperature endurance, cost-effectiveness, and sustainable utilization. Previous studies have investigated the advantages of MCF in terms of its processing and exceptional mechanical performance over a wide temperature range, however, superior inherent electrical conductivity and related piezoresistivity of carbon fibers (CFs) embedded within the matrix have not yet been explored systematically. In this study, we explore the utilization of MCF as highly sensitive stress sensors for structural health monitoring (SHM), including the electrical resistance, piezoresistivity, and underlying mechanisms of MCF composites under cyclic flexural stresses. Additionally, the effect of two different electrode configurations is examined. The findings reveal that the MCF exhibits a significant stress-sensing capacity under cyclic flexural loading within an elastic regime. Specifically, MCF with outer electrodes shows superior electrical conductivity, albeit with less significant fractional changes of resistance (FCR) and stress-sensing sensitivity. Conversely, MCF with inner electrodes exhibits the opposite trend. These outcomes provide valuable insights into the intrinsic self-sensing capability of MCF and propel its potential applications as a multifunctional composite, particularly in fields such as 3D-printed smart sensors and SHM for concrete infrastructures.