This article provides an overview of adult learning theory in relation to teaching philosophies among librarians belonging to ACRL, using Hadley's Educational Orientation Questionnaire. Although not significant as a predictor, there was a nonlinear and negative correlation between librarians' familiarity with the ACRL Standards and their adult learning orientation scores (p = 0.047, t < 0.05). Additional variables are included to investigate other influences on adult learning orientation scores. Results of the study showed high significance for gender (ß = 0.213, p = 0.008), current library instruction (ß = 0.199, p = 0.025), and the number of library instruction classes taught during the current year (ß = 0.199, p = 0.041). Additional descriptive statistical analysis and qualitative responses are included, and propositions for professional development are then introduced for future discussions among the ACRL community about the importance of adult learning as well as the evolution of our teaching philosophies.