Background and Purpose: Physical activity (PA) during the school day has proven to be an effective intervention to combat child and adolescent obesity. The purpose of this research was to utilize a mixed-methodological design to understand pre-service classroom teachers' perceptions of and self-efficacy towards physical activity during the school day. Method: Participants included 172 pre-service classroom teachers from 12 different universities in 11 different states in the USA. A 42-question survey was used to gather data on demographic variables, self-efficacy levels, physical activity habits, physical activity enjoyment, and comfortability implementing physical activity in the classroom. Data were analyzed through descriptive statistics, correlation analysis, regression analyses, and thematic analysis. Results: The analyses led to significant results for face-to-face general self-efficacy (M = 3.45, SD = 0.79) and virtual general self-efficacy (M = 3.24, SD = 0.90). Also, four themes resulted from the qualitative data: 1) Perceived Benefits of PA; 2) Preparation: Received and Not Received; 3) Personal PA: Then and Now; and 4) Pandemic Times: Pro or Con? Conclusion: Results showed an overall lack of in-depth preparation for pre-service classroom teachers and inconsistencies across the participating universities. Participant personal PA levels and personal PA enjoyment levels had a positive influence on their self-efficacy levels toward implementing PA. Increasing efficacy starts by helping pre-service classroom teachers think through and solve barriers that they might encounter when attempting to implement PA. [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.]