The student population is rapidly becoming culturally diverse. Math teachers are struggling to provide instruction responsive to student's cultural and linguistic strengths, which is the problem addressed in this study. The purpose of this interpretive phenomenological study was to explore the lived experiences of math teachers who instruct multicultural classrooms, specifically exploring challenges specific to math instruction and their influence on math teachers' competency to implement culturally responsive teaching. Hernandez et al.'s culturally responsive teaching model was used as a lens to help identify specific instructional challenges and suggestions to improve teachers' culturally responsive teaching competence. Seven math teachers who taught in urban high schools rich with cultural diversity were interviewed about their experiences teaching multicultural classrooms, their experiences with culturally responsive teaching, and its instructional challenges. The data was analyzed by hand using Smith et al.'s six-step interpretive phenomenology analysis. The findings disclosed teachers' unique lived experiences with different stakeholders, how the interactions indirectly influenced their culturally responsive teaching confidence or competence, and the extent to which it is implemented because it revealed their perceptions, depth of understanding, and personal attributes. It unveiled how much more the teachers struggled with culturally responsive teaching instruction in math than what was shared. However, the emphasis was not on the instructional challenges but rather on challenges like time or the lack of resources and training or teacher prep in culturally diverse settings. This led to implications of creating content-specific resources aligning to the culturally responsive teaching model to help meet the unique instructional needs of teachers. This study contributed to existing findings and further documented teacher attributes and behaviors to see how they influence culturally responsive teaching. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]