This study investigated multilingual writers' prior L2 writing knowledge transfer and how it relates to multilingual writers' metacognitive knowledge and metacognitive regulation. Specifically, this study aimed to 1) explore how multilingual writers transfer their prior L2 writing knowledge, 2) investigate multilingual writers' metacognitive knowledge and metacognitive regulation, and 3) examine how multilingual writers apply their metacognitive knowledge and metacognitive regulation to facilitate their prior L2 writing knowledge transfer. The participants were five undergraduates enrolled in a First-Year Composition (FYC) class for multilingual writers. The collected data to answer the study's research questions are thinking-aloud protocol, retrospective interviews, and students' first and final drafts of a major FYC assignment. The datasets were analyzed to explore multilingual writers' transfer of their prior L2 writing knowledge, their use of metacognitive knowledge and metacognitive regulation in their writing processes, and their utilization of the metacognitive knowledge and metacognitive regulation to facilitate their prior L2 writing knowledge transfer. The results showed that multilingual writers in this study repurposed, expanded, adapted, and reshaped their prior L2 writing knowledge. In addition, they integrated their recently learned FYC writing knowledge into their schema of prior L2 writing knowledge. Furthermore, findings showed that multilingual writers in this study utilized their metacognitive knowledge and metacognitive regulation as strategies for transfer. In particular, while transferring their L2 writing knowledge, multilingual writers utilized highly ranked metacognitive regulation moves, selective control and evaluative monitoring, to transfer their L2 writing knowledge. These findings expand the current metacognition and transfer theories. First, they provide a metacognitive dimension to theorizing prior L2 writing knowledge transfer of multilingual writers. In addition, these findings present empirical evidence that deepens the understanding of specific mechanisms of multilingual writers' prior L2 writing knowledge transfer. This study's findings also describe how specific metacognitive knowledge and metacognitive regulation facilitate prior L2 writing knowledge transfer. What is more, these findings provide a new theoretical framework for future research of multilingual writers' learning transfer. Lastly, these findings offer specific pedagogical recommendations to help multilingual writers transfer their prior L2 writing knowledge. [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.]