Anode-supported solid oxide fuel cells (SOFCs) offer the advantage of thinner electrolyte membranes which greatly reduce the ohmic loss and enables lower operating temperature and higher performance. However, a significant contribution to the polarization resistance is attributed to the anode, as the thickest component in the cell, which can influence the distribution of hydrogen partial pressure, p(H2) and water vapor pressure, p(H2O) especially when combined with current density to achieve high fuel utilization. To understand the degradation mechanism in long-term operation of a commonly used anode material, Ni/YSZ, commercial anode-supported cells were evaluated under varied current density (up to 1 A/cm2) and humidity (1-60%) using electrochemical impedance spectroscopy. The impedance spectra were analyzed using distribution of relaxation times (DRT) method to separate the resistance contribution from each component of the cell. The Ni/YSZ anode resistance was observed to increase with higher current density and humidity, suggesting that the degradation may be correlated to microstructural factors such as Ni agglomeration leading to reduced Ni interparticle contact, causing the increase in anode resistance. In addition, analysis using the 1-D transmission line model to determine the effective reaction length (ERL) of Ni/YSZ anode, revealed that the ERL moves further from the TPB with increasing degradation. Details of the post-test microstructural characterization of the cells will be discussed during the presentation.