This study evaluated a multi-parameter corrosion monitoring system for existing reinforced concrete structures in chloride-laden service environments. The system was fabricated based on a prototype concrete corrosion measurement system that had been built and patented by Southwest Research Institute (SwRI). In a laboratory benchmark test, a chloride concentration vs. potential calibration curve was established and indicated good linearity between 0.01 mol/L and 1 mol/L. The general and maximum localized corrosion rates, as measured by the Multi-electrode Array Sensor (MAS) probe, were all sensitive to the incremental chloride concentration in a simulated pore solution. However, once active corrosion is initiated and a great amount of chloride is present, the MAS probe may no longer serve as a good tool to predict the corrosion rate of rebar unless more research is conducted to establish such prediction or correlation. It was also revealed that in a sensor longevity test, only a fraction of sensors can be considered reliable after eight accelerated weathering cycles. In addition, a laboratory pilot-scale test was done by incorporating an array of three sensing units at different depth of a mortar cylinder to monitor the ingress of chloride and the corrosion rate of rebar at different depths. The results identified many challenges to improve the sensor probe. A detailed guideline along with video documentation was developed as a reference to guide field implementation. A field deployment of the system in an Oregon Department of Transportation (ODOT) bridge pier was attempted for a few months. However, future research into improvements of the sensor system is needed to achieve a successful field application.