This study examines potential bias with respect to perceived gender and ethnicity in preservice teachers' professional noticing of children's mathematical thinking. The goal of the study was to explore how, and to what extent bias emerges within pre-service teachers' professional noticing of children of differing perceived races and genders. Our findings suggest that bias tends to emerge in the interpreting phase of professional noticing; however, such emergence did not appear to vary in conjunction with the perceived ethnicity and gender of the student. Further, our findings suggest that the inclusion of visual imagery (i.e. photos) influence the manifestation of bias among preservice teachers to some degree when professionally noticing in the context of a written case.