The purpose of this quantitative correlational study was to determine if and to what extent a relationship exists between K-12 principal and assistant principal cognitive, affective, and behavioral attitudes towards inclusive education and overall attitudes toward inclusive education in schools in the United States. The theoretical foundations for this research included Planned Behavior Theory. The study was guided by three research questions which sought to examine if a relationship exists between principal and assistant principal cognitive, affective, and behavioral attitudes toward inclusive education and principal and assistant principal overall attitudes toward inclusive education in schools. A convenience sample of 113 K-12 principals and assistant principals were recruited through members of two Facebook groups. Participants completed an online survey which included a demographic questionnaire, the Principal Attitudes Toward Inclusive Education Survey (PATIE) and the Multidimensional Attitudes Toward Inclusive Education Survey (MATIE). The results of a nonparametric Kendall's Tau-b correlation, evaluated at a corrected [alpha] < 0.016, were as follows; cognitive: t[subscript b] = -0.268, p < 0.000; affective: t[subscript b] = -0.234, p < 0.000; and behavioral: t[subscript b] = 0.137, p = 0.052. The results found a statistically significant relationship between principal and assistant principal cognitive and affective attitudes and overall attitudes toward inclusive education. These findings justify further research in the relationship between principal and assistant principal multidimensional and overall attitudes toward inclusive education. [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.]