Flicker glare and visual comfort of multicolor LED billboards are investigated in this study. The influences of two factors, flicker frequency and panel luminance, on visual discomfort and tiredness are examined. Results of ergonomic assessments show that visual comfort is affected by the flicker frequency and luminance, but visual tiredness is not influenced by either factor. By curve fitting the experimental data, comfort rating models as functions of the flicker frequency and luminance are proposed. Furthermore, the ranges of proper operating conditions are suggested based on the predictions of the proposed models.