Purpose: The purpose of this study was to identify key strategies for designing professional development for teachers of blended high school courses, as perceived by California high school principals. High schools are going to the blended model more frequently and the trend is that there will be many more such models for high school students as technology becomes more accessible to students. This study fills a gap in the literature and informs principals about various strategies to help develop teachers to better serve their student populations. Methods: An extensive review of the literature yielded the theoretical framework that central to effective teacher professional development is three characteristics: it must be intentional, ongoing, and systemic. Educational leaders of schools with blended courses responded to interview questions using the dynamic narrative approach in order to identify key strategies. The participants were California high school principals of blended schools. An expert panel of researchers contributed to establishing validity and interrater reliability was used in data analysis. Findings: The study identified key strategies for designing professional development for teachers of blended high school courses for each category outlined in the theoretical framework: intentional, ongoing, systemic. The research resulted in a total of 19 overarching key strategies: 6 for intentional, 6 for ongoing, and 7 for systemic. Conclusions: A well-trained teacher can potentially expand upon the online components of the blended classroom. Research indicates that better student achievement can be reached in a blended environment than traditional educational counterparts, which can lead to higher test scores, resulting in more financial options for school administration. Students achieve more academically if their teachers are well versed in the pedagogical strategies and techniques necessary for blended learning. Recommendations: Further research in this field is needed to focus on different stakeholders in the high school setting. This type of study may highlight what students believe make teachers effective after having engaged in professional development. Researchers could also look at specific pedagogical activities used in blended settings and the professional development used to train in these techniques. [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/en-US/products/dissertations/individuals.shtml.]