Teacher recognition of student argumentation has been addressed by many researchers (e.g., Schwarz, 2009; Krummheuer, 1995; Bieda & Lepak, 2014; Whitenack & Yackel, 2002). Further, standards for mathematics learning emphasize the importance of including argumentation in the K-12 classroom (NCTM, 2000; CCSS, 2010). The study reported here with secondary preservice teachers to identify argumentation from video, adds to earlier, successful work using video to support the learning of preservice teachers (Sherin & Han, 2004) and to support teacher noticing (Van Es & Sherin, 2008; Star & Strickland, 2007). Further, studying video narratives has been used effectively in university courses to encourage students to engage with complex issues, collaborate, discuss, and build representations, and can help instructors gain insight into student thinking (Hmelo-Silver et al., 2013). This qualitative case study examined the effect of a semester-long intervention with eleven preservice teachers during the spring of 2015. Episodes of student argumentation from the Video Mosaic Collaborative (VMC), an open-source video collection, were used to construct video narratives using the RUanalytic Tool (Agnew, Mills, & Maher, 2010) of students engaged in argumentation. Findings from this study indicate that video narratives supported growth in the preservice teachers' understanding of student argumentation, indicating that for 93.3% of the events in the study, at least 45% of teachers exhibited growth and for 73.3% of the events in the study, at least 54% of teacher exhibited growth. Teachers demonstrated growth with respect to: (1) the elements of argumentation and (2) the structure of the argumentation they described; as well as (3) the use of the technical language of the formal mathematical register of argumentation they used. Other changes included making implicit argumentation explicit, using students' actual language rather than interpreting students' statements, and eliminating untrue statements about the argumentation in the events. Furthermore, there was a relationship among the categories, for example, the growth in use of technical language correlated to both growth in elements and growth in structure. Implications of the study and future research recommendations include comparing the results of other iterations of the study and using VMCAnalytics to support other mathematical practices. [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.]