Interpreting Albert Bandura's term "self-efficacy" as the individual's belief in his own abilities to succeed in spite of the given circumstances, this study seeks to identify the influences which lead to self-efficacy in Montessori teachers. In order to evaluate perceptions of self-efficacy, 35 pre-service teachers in the United States were surveyed prior to beginning their Montessori teaching and again during the internship stage of their training. As Bandura asserted that self-efficacy stems from four possible sources: mastery experience; vicarious experience; verbal or social persuasion; and physiological state (1997), the same subjects were given an additional questionnaire to determine which factors most affected their efficacy. Multiple regression was then used to examine the relationship between those factors and the teachers' self-reported efficacy. Following this data collection, four teachers from the high self-efficacy group and four teachers from the low self-efficacy group were interviewed to reveal detailed qualitative information regarding the influences on their classroom efficacy. The research indicates that Montessori teachers with high levels of self-efficacy have strong mastery experiences that support their attitudes and desired professional goals. The quantitative results also show that an emotional state associated with past experiences is the second best contributor to self-efficacy. Considering that self-efficacy may be most malleable during the early stages of learning, the results of this study serve to enhance the teacher-training experience though the analysis of early obstacles. [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.]