The field of information literacy (IL) suffers from a gap between theory and practice, meaning that librarians, as practitioners, do not adequately use and apply the theory of information science in their work (Hider et al., 2019; Julien et al., 2013; Nguyen & Hider, 2018). Specifically, IL is theorized as a social practice, yet practitioners appear to adopt a skills-based approach to IL. As an answer to this theory-to-practice gap, a grounded theory study found that seeing information literacy as a social practice is a threshold concept for academic instruction librarians. This dissertation study employed focus groups and semi structured solicited diary prompts to explore the fit of this threshold concept with the experiences of academic librarians. The central research question for this study was: To what extent, if any, does the proposed threshold concept describe librarians' beliefs about information literacy as a social practice? Qualitative content analysis of the focus group transcripts and the diary entries found that the threshold concept required a slight revision in order to accurately describe librarians' beliefs about information literacy as a social practice. Where the initial version of the threshold concept had one arrow indicating "tensions" that prevent librarians from teaching IL as a social practice, the revised version contains an opposing arrow indicating "supports" that help librarians to deliver IL from a social practice standpoint. In addition to this change, the role of skills and practices in IL instruction were investigated. Findings from this study have implications for library and information science educators, library administrators, practicing academic instruction librarians and students. [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.]