Teachers’ professional noticing—often conceptualized as their situation-specific skills of perception, interpretation, and decision-making—constitutes an important component of their professional competence. Noticing has become increasingly significant worldwide in the pursuit of inclusive mathematics education in classroom settings, whereby teachers are required to provide equal opportunities for students. However, current teacher noticing frameworks lack the requisite specificity to support inclusive mathematics education, particularly regarding diagnostic applications and adequate learning support, and thus a revision of existing frameworks is warranted. On the one hand, such frameworks must incorporate selected facets of teacher knowledge, including mathematical pedagogical content knowledge (MPCK) and general pedagogical knowledge (GPK) specified for inclusive teaching; on the other hand, the differentiation into dispositions and situation-specific skills as decisive components of competence viewed as a continuum must be considered, as Sigrid Blömeke et al. suggested in their seminal framework. Using a large sample of 628 pre-service and in-service teachers, this paper aims to examine the dimensionality of teachers’ competence for inclusive mathematics education and expert–novice differences in the pattern of their competence facets. For that purpose, knowledge tests and video-based instruments for assessing teachers’ noticing in inclusive mathematics education among pre-service and in-service teachers were newly developed. Empirical findings provide evidence for the hypothesized dimensionality of teacher noticing in knowledge and skills as well as mathematics and general pedagogy. However, against our expectations, in-service teachers did not outperform pre-service teachers. We discuss such counterintuitive findings towards their implications for teacher education design and future test development.