In the future, a major role of fuel cells in combined heat and power generation systems is envisaged. It is well known that a fuel cell's efficiency is highly dependent on the operating conditions, such as temperature, humidity, and air flow. In the aim to assure optimal operating conditions as well as to minimize the losses, parameter identification, diagnostics, and control are going to play an important role. The paper deals with parameter identification and diagnostics of a low-power proton-exchange membrane fuel cell considering a system identification approach. This multi-input multi-output electrochemical system can be tested or monitored by identifying its parameters, which has real importance in the manufacturing, exploitation, and maintenance phase. Therefore, parameter identification represents the core of any diagnostics or online monitoring procedure. Furthermore, online parameter estimation might be used for control purposes to maintain the fuel cell in an optimal operating point with minimal losses. The proposed parameter identification method is simple, cost-effective, and can be extended easily for fuel-cell stacks too.