This study is an in-depth investigation of the National Board for Professional Teaching Standards (NBPTS) bias-reduction training, from the perspective of assessors. The research examined how successful the bias training was in guiding assessors to recognize their biases and to identify actions to be used to reduce the impact of bias on their scoring decisions. The study focused on portfolio video entries to allow for a greater exploration of bias, since assessors are provided with a visual and aural depiction of the candidates and their students.