In this study, conventional and dynamic electrochemical impedance spectroscopy measurements (EIS and DEIS, respectively) were performed on Ir(111) single crystal electrode and Ir nanoparticles supported onto high-surface area carbon in acidic electrolyte and different potential ranges. We found that the EIS and DEIS results compare fairly well below the onset of oxygen evolution reaction (OER). However, in the OER potential region, some differences were observed between the information derived from these measurements. Cyclic voltammetry and inductively-coupled plasma mass spectrometry experiments revealed that the long time required by EIS cause chemical and structural changes of the Ir(111) surface and oxygen evolution, thus adversely affecting the reliability of the impedance measurement. On the contrary, the short time required for DEIS measurements help mitigating these negative effects, thus highlighting the benefits of such technique to investigate the early stages of surface oxide formation on Ir single crystals.