All rights reserved.iv DEDICATION Mamí. Nunca tuvo acceso a una educación formal. Sin embargo, se sacrifico con el fin de que mis hermanos y yo lo haría. Su ejemplo, bondad, humildad, sabiduría y oraciones son las razones que puedo escribir estas palabras. Doy gracias a Dios por honrarme con una madre como la mía.To Nathan Boveda, my best friend. Thank you for being an exemplary father to our children and our loves: Leah, Nathan, and Nicole. Thank you for loving my mother as she was your own and collaborating with her to support and sustain me during this journey. Thank you most of all for your integrity. Intersectionality theory explores the complexities of the interactions of multiple markers of difference. Intersectionality holds great potential as a concept for preservice teachers' understanding of diversity because it can inform collaborative efforts with diverse stakeholders, enhance preservice teachers' understanding of diverse learners, and facilitate an integrated treatment of diversity in teacher preparation research. The researcher uses the term "intersectional competence" to describe preservice teachers' understanding of diversity and how students, families, and colleagues have multiple sociocultural markers that intersect in nuanced and unique ways.The purpose of the study was to identify the indicators that best capture intersectional competence and to develop and validate an instrument that measures preservice teachers' intersectional competence. The researcher drew from the literature on intersectionality in special education, the research on collaborative teacher preparation, and assessments of preservice teachers' understanding of diversity to viii identify indicators of the intersectional competence construct. The instrument included two subsets of items. Subset A was a survey designed for preservice teachers to selfreport their intersectional competence and Subset B consisted of items of a case-based measure of preservice teachers' intersectional competence. A mixed-methods sequential exploratory research design was used to develop and validate the instrument.During the qualitative phase, the researcher collected data that strengthened the theoretical basis for validating the instrument (i.e., interviews with focus groups, consulting with experts, and cognitive pre-testing). Throughout the qualitative phase, general education and special education preservice teachers were able to recognize and discuss the complexities of intersecting sociocultural categories. The second phase of the study involved the quantitative analysis of the validity and reliability estimates established for the instrument and the piloting of the items with 107 participants. The piloted draft of the ICM was upheld to be a reliable tool to assess whether preservice teachers are adequately competent to meet the needs of a complex and diverse school population. The feedback about each subset of the pilot of the ICM, as well as feedback about the instrument as a whole, indicate that the ICM will require further development a...