Multicultural education emerged over three decades ago as a reform movement to address the inequities in schools that lead to disparate outcomes and experiences among marginalized students. However, the extent to which these aims have been realized has yet to be assessed. Although multicultural efforts are common, they are also inconsistent and often superficial (Banks, 2007; Cochran-Smith, 2003; Gay, 2002; Ladson-Billings, 2004; Sleeter, 2012). This, in turn, impacts teachers’ ability to address the aims of multicultural education in their classrooms. Thus, this present study sought first to operationalize what it means to be a multicultural teacher and then to develop and examine the psychometric properties of the Multicultural Teacher Capacity Scale (MTCS). The MTCS assesses the extent to which teachers promote equity within their classrooms and beyond as described by 11 characteristics described along a continuum of five progressive levels. The instrument development and validation process involved three phases: instrument construction, instrument review and revision, and instrument evaluation. These three phases were designed to examine six hypotheses, of which three were adequately supported and three were not. The 11 characteristics were consistent with culturally relevant and culturally responsive pedagogies and agreed upon by field experts. The MTCS demonstrated adequate internal consistency. Exploratory factor analysis results suggested an 11-item, two-factor solution: (1) beyond classroom context and (2) within classroom context. The results from an Item Response Theory analysis did not sufficiently support the matrix design of the MTCS due to sample size violations. The characteristics captured a limited range of multicultural teacher capacity ability levels, with more items needed to capture higher ability levels. Teacher responses revealed a proclivity towards social desirability. The MTCS is a reliable and valid measure of multicultural teacher capacity for samples that mirror the development sample. The instrument should continue to be evaluated and refined to gather further support for use as a measure of multicultural teacher capacity. At present, the use of the tool is perhaps best suited for stimulating self-assessment and reflection for educators, informing teacher preparation programs, and guiding professional development.