Classroom-based physical activity (CBPA) is a proven strategy for increasing students' physical activity (PA) levels. Classroom teachers play a vital role in the effective implementation of CBPA. The socioecological model (SEM) emphasizes that institutional and intrapersonal factors influence the viability and sustainability of CBPA. However, there is a paucity of research examining specific intrapersonal factors that influence CBPA. This study aimed to address a gap in current literature by exploring how the intrapersonal factors of elementary classroom teachers' personal PA behaviors and their attitudes toward school-based PA related to their practices of PA integration in the classroom. This cross-sectional correlational design utilized an online survey containing validated instruments: the International Physical Activity Questionnaire-Short Form (IPAQ-SF; Craig et al., 2003), the Physical Activity Promotion in the Academic Classroom questionnaire (PAPAC; Webster et al., 2013a), and the School Physical Activity Promotion-Attitudes Questionnaire (SPAP-AQ; Webster et al., 2010). The surveys were distributed to classroom teachers in K-6 grade and yielded 145 responses. Significant relationships were observed between the teachers' PA behaviors, their attitudes toward PA promotion, and their practices of CBPA. Teachers' current grade level and their participation in moderate and vigorous intensity PA were predictors of CBPA integration. Teachers' intrapersonal factors also influenced their CBPA integration. Increased efforts must be made to provide teachers not only with the education, field experience, professional training, and resources to become advocates for and regular users of CBPA, but also with the knowledge, opportunities and skills to personally engage in regular PA and reap the benefits of healthy living. [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.]