Multimodality describes the nature of social semiotics as including multiple modes such as speech, writing, image, gesture and sound. Accordingly, multimodal literacies refer to the practices and texts utilizing these modes, while social semiotics frames these multimodal literacies as meaningful sociocultural practices (Kress, 2010). Multimodal literacies have been incorporated into various content areas for instructional purposes, but research in the multimodality of mathematics instruction often lacks the sociocultural lens. The following describes a study in which the nature and use of multimodal literacies in a secondary mathematics classroom was explored through case studies of six participants by analyzing projects, work samples, classroom video footage and interviews. The study explored the ways in which multimodal literacies enabled students to exhibit agency in their learning of mathematical content. Particularly of interest is how students utilized multimodal literacies to negotiate their figured world (Gee, 2014) of mathematics. The study used a social semiotic framework and multimodal analysis of classroom video footage, student interviews, projects, Edmodo online forum discussions and written assignments. The findings reveal ways in which multimodal literacies may serve as a vehicle for students to engage with their social context of learning in a mathematics classroom by creating a classroom community. This community was evidenced by five sub-themes including the teacher as a valuable facilitator, connections and interactions between students, incorporation and validation of student identity, communication of perceptions and feelings surrounding mathematical content, and finally, learning effective communication for purposes of explaining and justifying. As a result, a community was created in participants' figured world of mathematics which allowed for them to have deeper understandings of the purposes and structures of mathematical content. With this understanding, participants also related mathematical content to real-world applications and other content areas in ways they had not necessarily considered before. This demonstrates that a sociocultural approach to multimodal literacies can be relevant for incorporating students' out-of-school literacy practices and content literacy strategies into mathematics, thereby apprenticing students into disciplinary literacy practices of mathematics. Moreover, this learning community for multimodal literacies inspires a need for research regarding possible applications of instruction in multiple content areas. [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://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]