An experimental investigation was performed on a NACA 0012 airfoil with simulated three-dimensional and two-dimensional leading-edge glaze ice accretions. The unsteady flow features were investigated through spectral, correlation, and visualization analyses and were related to the iced-airfoil performance. The most significant unsteady flowfield effect on the iced-airfoil performance was a low-frequency flow phenomenon on the order of 10 Hz that resulted in Strouhal numbers of 0.0048 – 0.0101. The low-frequency oscillation produced large-scale pressure fluctuations near separation at high angles of attack and elevated lift and moment fluctuations as low as a = 5º. The iced-airfoil flowfield exhibited a separation bubble of varying thickness and fluctuating reattachment, characteristics similar to those associated with the low-frequency shear-layer flapping and bubble growth and decay of other separated and reattached flows. Vortex structures observed in the shear layer were presumed to be the cause of large-scale pressure fluctuations upstream of reattachment at small angles of attack. Pressure spectra near reattachment exhibited wide bandwidth frequency peaks that indicated a non-periodic phenomenon and corresponded to the regular mode often associated with vortex movement in and aft of the shear layer. Strouhal numbers ranged from 0.53 to 0.73. Although vortex shedding was rarely observed, the convection of surface pressure fluctuations occurred at approximately half the freestream velocity, similar to shedding velocities reported by others.