Many science teachers leave the teaching profession during the first five years of practice resulting in a "greening" of the population. This phenomenon produces a high concentration of early-career teachers with low levels of pedagogical content knowledge (PCK). PCK is the ultimate measure for knowing the content one teaches and the best strategies to transmit the knowledge. Teachers develop PCK through experience grounded in reflection. Yet, teacher preparation programs provide little experience with authentic, reflective practice leaving newly hired science teachers with limited understanding of the content and how to teach it to students. Research shows promise for increasing levels of PCK using multiple methods of support and professional development, but researchers know little about how this development occurs. While many researchers focused on planning, some were more concerned with enactment. However, few studies addressed the complete planning, enacting, and reflecting teaching cycle. Understanding how PCK develops may lead to more effective methods of early training. This study examined the role of coaching or mediated instructional support on an early-career chemistry teacher, PCK development, and the role of mediated reflection during the process of uncovering knowledge transfer. Findings revealed (a) the importance of the positioning of the coach, (b) a pattern of reflective steps necessary for effective PCK development, and (c) a pattern indicating a link between content knowledge, the expression of content understanding, and the alignment of content understanding with instruction for successful PCK development. [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.]