The combination of infrared (IR) spectroscopy and electrochemistry in a single measurement has been an area of active research interest since the late 1960s. IR spectroelectrochemical experiments provide insight about interfacial electrochemical phenomena and/or oxidation–reduction reaction mechanisms that cannot be obtained using either technique individually. The power of the measurement is in the complementary nature of the spectroscopic and electrochemical information available when obtained simultaneously. The combination of measurements, however, requires compromise between the IR spectroscopy and the electrochemistry because of their different sampling requirements. The need for compromise illustrates the unique strengths and weaknesses of the combined spectroelectrochemical measurement. Three spectral sampling methods are commonly used: transmission, internal reflection, and specular reflection sampling of the electrochemical experiment. Additional experimental perturbations, such as polarization and electrode potential modulation, are frequently applied to increase the spectral sensitivity toward changes confined to the electrode interfacial region. This article presents the instrumental requirements for, and a theoretical background of, different types of IR spectroelectrochemical measurements.