The purpose of this study was to understand how a science, technology, engineering, and math (STEM) professional development workshop improved teachers' self-efficacy and motivation to implement STEM in their afterschool programs as well as develop a tool that measures STEM motivation and self-efficacy. Educators' self-efficacy and motivation were measured using the proposed instrument before and after they attended a professional development workshop centered around an engineering design activity. Quantitative data were collected and analyzed over four phases. A proposed instrument measuring two constructs, self-efficacy and motivation, was implemented, analyzed by factor analyses, and refined until a final instrument version was created. Findings indicated that there is sufficient evidence to support the validity of the proposed instrument. While there is sufficient evidence of validity, future research should be conducted to improve the validity as well as better conceptualize educator self-efficacy and motivation regarding STEM implementation. Implications from this study have the ability to improve professional development design and practice as well as encourage educators to implement STEM focused curricula in afterschool by increasing their confidence and motivation to do so. This research also adds to the existing literature by providing information about educators' needs and attitudes around STEM education. Lastly, this research has the ability to inform practitioners, stakeholders, researchers, and policymakers about how to motivate afterschool program staff to effectively provide integrated STEM learning with confidence. [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.]