Learning to teach is multifaceted and dynamic resulting in a turbulent, fast-changing era of professional life for early career science teachers (ECSTs). Teaching practice is uncertain and tensions are endemic to the profession (Ball, 1993). This dissertation connects to and extends current research of the challenges ECSTs face and how those challenges affect ECSTs' work, identity, and experience. In the first chapter, I introduce my research focus and offer a personal narrative to provide context of my positionality and experiences between myself and my research. In Chapter 2, I offer a systematic review of the literature to provide a contemporary update to Davis and colleagues' (2006) review "Challenges New Science Teachers Face" to answer the question: "What challenges do ECSTs face while navigating their first years of teaching?" Chapter 3 describes the research design, data sources, and general analysis for the longitudinal case study of an ECST, Alexa. The remaining body chapters build upon Chapter 2 and each other in answer to my remaining research questions: "What challenges does Alexa face as an ECST?" "How does Alexa's teacher role identity develop over time?" "In what ways do challenges shape Alexa's teacher role identity?" Chapter 4 builds upon the themes drawn from Chapter 2's systematic review to explore the challenges Alexa experiences. Chapter 5 describes how Alexa's identity develops across her early years as an ECST using a Dynamic Systems of Role Identity framework (Kaplan & Garner, 2018). Chapter 6 explores how those challenges impacted Alexa's science teacher identity using a productive friction framework (Hagel & Brown, 2005a). In Chapter 7, I close by summarizing the research, describing its implications, and offering future directions for research and practice. [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.]