The purpose of this sequential explanatory mixed-methods study was to investigate school librarians' self-efficacy in the multiple literacies. This study was conducted to develop an understanding of the role of librarians in the multiple literacies, and what they feel has an impact on their capacity to implement multiple literacies practices. Research Question 1 (QUAN): What are the self-efficacy beliefs of school librarians with regard to the teaching of the multiple literacies? Research Question 2 (qual): How do school librarians describe their self-efficacy beliefs and experiences in the multiple literacies? Mixed-Methods Research Question: In what ways does the qualitative interview data of school librarians' self-efficacy beliefs and experiences in the multiple literacies help to explain the overall results of the quantitative data on librarians' self-efficacy beliefs? A total of 117 librarians provided responses to a survey that addressed this research question. The sample was primarily female (94.9%), with a majority (57.3%) working in high schools. With the exception of one participant who was under 30, the ages of participants were evenly distributed from 30 to over 58 years old, and the majority (52.1%) had over 11 years of experience. According to the results of an ANOVA analysis, age and experience did not make a difference in the self-efficacy beliefs of participants with regard to teaching multiple literacies. This indicated that librarians of all ages and levels of experience felt similarly self-efficacious across multiple literacies domains and across demographic grouping in their abilities to use and provide instruction in the multiple literacies. This differed from Koenig and Eagly's view that school librarian stereotypes are rooted in fact (2014). The second research question reflected the qualitative phase of this study. Five participants were selected from the total sample of 117 librarians to participate in semi-structured interviews for this phase of the study. The results of the qualitative portion of this study reveal that the themes of: (1) Socialization and (2) Performance occurred during participant interviews. Subthemes observed in this study include: (1A) social persuasion, (1B) engagement, (1C) physiological factors, (2A) experience, and (2B) modeling. The theme of Socialization was the most prevalent during respondent interviews, indicating that perceptions of self-efficacy more significantly focused on social observations and beliefs than actual performance measures. In spite of widespread under-recognition and underuse related to multiple literacies instruction, librarians remained steadfast in their self-efficacy beliefs in this area. Formal education and training, along with success experiences with students bolstered participants' self-efficacy beliefs with regard to instructing in the multiple literacies. However, an overwhelming response was that these abilities are not sufficiently recognized and used in their schools. The findings of this study highlighted the valuable resource librarians represent, and their potential to enhance student learning and mastery of the multiple literacies. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]