The purpose of this quantitative correlational-associative study was to examine if and to what extent a relationship existed between collective teacher efficacy and teachers' attitudes toward inclusion in the American Midwest. The sample consisted of 165 K-12 teachers who had accounts with Centiment. Social cognitive theory provided the theoretical foundation for this study. The Collective Teacher Beliefs Scale and the Attitude Towards Teaching All Students instrument were used to measure the variables. Four research questions were posed for the study: if and to what extent does a relationship exist between collective teacher efficacy and teachers' overall attitude toward inclusion; cognitive attitude toward inclusion; affective attitude towards inclusion; and behavioral attitude towards inclusion. Spearman's correlation analysis indicated that a statistically significant negative correlation existed between collective teacher efficacy and teachers' overall attitudes toward inclusion (r[subscript s] (165) = -0.216, p < 0.01), affective attitude toward inclusion (r[subscript s] (165) = -0.205, p < 0.01), and behavioral attitudes toward inclusion (r[subscript s] (165) = -0.261, p < 0.01). Pearson's correlation analysis did not indicate a statistically significant correlation for the relationship between collective teacher efficacy and teachers' cognitive attitude toward inclusion (r (165) = -0.14, p = 0.064). The conclusions indicate that collective teacher efficacy should be explored further as a means of supporting positive attitudes toward inclusion, and therefore, contribute to the implementation of effective inclusion programs. The findings are important to the field of education where negative teacher attitudes toward inclusion persist despite the integral role that teachers play in the successful implementation of inclusion programs. [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.]