An in-situ technique is presented for measuring the individual contact resistance between the pin of an IC package and the board of a flexible hybrid electronic system. As the substrate flexes, the forces that adhere the IC to the substrate change and cause increase to the series contact resistance; sometimes catastrophically. Tracking this resistance is seen to be fundamental to the success of electronic systems mounted on a flexible substrate subjected to various levels of bending. The measurement technique utilizes priori information about on-chip ESD protection circuits as a means to isolate the contact resistance. While the series contact resistance can be measured with a four-point Kelvin measurement, it is extremely difficult to perform with small surface-mount IC packages. The experimental results pertaining to Kapton-polyimide substrate subjected to a controlled bending process will be described. The method proposed here determines the contact resistance with a relative accuracy error of less than 1%.