The electrode temperature distribution of a solid oxide fuel cell is an important parameter to consider for gaining better insight into the cell performance and its temperature-related degradations. The present efforts of measuring gas channel temperatures do not accurately reveal the cell surface temperature distribution. Therefore, the authors propose a cell-integrated multi-junction thermocouple array to measure the electrode temperature distribution from a working solid oxide fuel cell. In this work, the authors deposited a thin film/wire multi-channel thermal array on the cathode of a commercially-sourced solid oxide fuel cell. The temperature of the cell was measured under varying fuel compositions of hydrogen and nitrogen. The multi-channel array showed excellent temperature correlation with the fuel flow rate and with the cell's performance whilst commercial thermocouples showed a very dull response (10 similar to 20 degrees C discrepancy between thermocouples and the multi-channel array). Furthermore, cell temperature measurements via the multi-channel array enabled detecting potential fuel crossover. This diagnostic approach is applied to a working solid oxide fuel cell, yielding insights into key degradation modes including gas-leakage induced temperature instability, its relation to the theoretical open circuit voltage and current output, and propagation of structural degradation. It is envisaged that the use of the multi-thermocouple array techniques could lead to significant improvements in the design of electrochemical energy devices, like fuel cells and batteries and their safety features, and other hard-to-reach devices such as inside an internal combustion engine or turbine blades.